The only people who try to keep others of us out of their meetings or gatherings, or even discussions in certain areas of certain forums (any Rand, or voting in general, criticism), are the minarchists. The "purists" aren't using any coercion to keep minarchists out of meetings, gatherings, or discussions. Anarchists have no problem with minarchists showing up to our events or voicing their opinions (they do at every one of them)...it's the minimalist state socialists (the capitalists who want small government) who try to ignore, alienate, or discourage the "purists" (those who want a pure free market society, not minimalist state socialism). The "purists" just point out the bullshit being spewed as rationalizations for not taking the ideas of liberty, free markets, property rights, free expression, free association ,etc., etc., etc. to their logical conclusions.
One side claims to want diversity and tolerance while actively trying to shoo away anarchists. The other side (anarchists) don't shoo anyone away, but just insist on calling out bullshit arguments for immorality when we hear them.
Which is really intolerant or against diversity?
The only people who think purism in libertarianism is bad are the people who aren't taking libertarianism to its logical conclusions (and therefore aren't taking it completely seriously). This cognitive dissonance and lack of consistent logic, and therefore ethics, leads to them to actively trying to hide anarchists away from public eyes by not associating themselves with us (
even though we popularized the word "libertarian" after the word "anarchist" was banned in print), actively seeking to not invite us places, marginalize our ideas via hyperbole or other logical missteps, and look at us like the black sheep of the liberty family.
I don't know of a case in this movement where anarchists have said "no minarchists allowed"...but I know of several cases where minarchists said "no anarchists allowed - or if you come, you can't talk about anarchism as we suck-off the state for a few hours" (of course, that's a paraphrase).
This is something libertarianism has to come to terms with; do we want to grow our movement fastest by misrepresenting the philosophy or philosophies therein via the exclusion of its founding faction (and its intellectual foundation)? Or do we want to forego a bit of speed in our race to grow the number of people who embrace these ideas in favor of intellectual honesty, the market of ideas, and embracing the founders and backbone of our movement?
The "purists" founded libertarianism, and they are the suppliers of its intellectual ammunition. The "purists" aren't excluding anyone...we're just calling people out on their bullshit and inconsistencies. All the exclusion and intolerance is coming from the non-purists. Calling someone out for logical or ethical or economic inconsistencies doesn't exclude them. It may upset them, but truth is often painful. Shall we just allow people to live in the bliss of their ignorance when it victimizes innocents to do so? I don't think so.
If someone wants anarchists to keep quiet, then start another movement. Anyone can claim to be a dog or cat, or libertarian for that matter...but it doesn't make it so, just because they claim it. We won't exclude people or tell them to stop calling themselves libertarian, but we will explain to them why their ideas about limited government aren't consistent with reason, logic, and therefore ethics in libertarianism. They can keep those ideas if they like...but if we ever get to a small government they want, they will quickly find the anarchist "purists" who were once their allies will then be their bitter enemies.
Hence violent revolution for anarchists is garbage and useless. You'll allow us to help you win the revolution, and then when its time for us to part ways on whether a new state should be set up to legalize criminality like extortion and murder for some tiny minority parasitical ruling class, you'll label us enemies of the new state and have us tortured, murdered, blackballed, kidnapped, and/or deported. That's the outcome historically every time we aid minarchists or any other form of revolutionary. They turn on us as soon as its a choice between liberty and free markets, or the state. They value minimalist (or worse) state socialism too much to give up socialization, and therefore subsidization by the unwilling, of roads, defense, police, and law (among other things, depending on how minimalist their state socialism is).
We're keenly aware that our allies today will likely be our enemies when the moment of truth comes and it really counts. But it won't be us excluding anyone. We simply rather grow more slowly and sustainably, rather than bullshit or keep others from facing arguments that take things to their logical (and therefore ethical) conclusions. The latter will grow faster and win elections quicker, but it's not sustainable. The watered down libertarian movement will then elect watered down libertarian politicians, and therefore they will make statist errors which will be rightfully blamed on them, turn people off to libertarianism, and set us back. It's like the Business Cycle...minarchists want to expand the money supply (libertarian voting base) as quickly as possible with no regard to the bubble effect it causes. The anarchists want to expand the money supply (libertarian voting base) only as fast as the market (philosophical spectrum of the masses) dictates, in order to avoid a bubble. Minarchists would be happy to bullshit people into voting for libertarian candidates as long as they won more seats (see Rand's so-called stealth strategy). Anarchists don't focus on voting totals (and in some cases, voting at all)...we focus on changing hearts and minds of the masses to libertarian philosophy (a 2nd Enlightenment). We'll get to the higher vote totals as a result of that, and it won't be a political bubble ready to burst.
Mark my words: you'll win more and faster your way...but the bubble will burst and the ebb and flow of seats will come, as it does for the other full of shit ideologies already dominating politics. Our way is more sustainable, has less severe swings in the ebb and flow of seats, and will take longer but gain more long term traction. Why? Because if you truly change minds to libertarian philosophy, even when they are incapable of taking their newly embraced ideas to their logical (and ethical) conclusions, then the ebb and flow of voting patterns are less volatile. People don't usually convert away from libertarianism IF they come to it honestly and are exposed to the more radical elements who preach the "pure" form of the philosophy (even if they end up falling short of agreeing with us). It's the radical element the moderates seek to temper themselves against...and without it being purely expressed, they will temper their ideas on less radical ideas, be less radical themselves therefore, and thereby less attached to the ideas they claim to embrace. The level to which they are convinced by, and committed to, the movement will be less when they are bullshitted or sheltered, which makes them less ideologically attached to the actual tenants of the philosophy. If the level of convincing and committal is high enough, via exposure to the most radical and truthful, and the most moderate alike, and allowing these ideas to take root as radical, moderate, or something between, then the person is unlikely to abandon libertarianism in the future.
Every asshole I've ever met who said he "used to be a libertarian" didn't read many libertarian authors, never read anarchists in depth, and never really was a libertarian (other than in label) to begin with. Those who come to the philosophy honestly, through debate and research, trial and error, open-mindedness and time, never leave it...it's got too much truth to abandon it. Anyone with a conscience can't be privy to the logical, and therefore ethical, truth in libertarian thought, and then simply walk away from it in favor of everything we stand against. It's nearly impossible to make such a reverse-conversion (reversion). But if one doesn't come to libertarianism the right way, then of course they can take it or leave it anytime it's convenient for them personally.
Faux or half-assed libertarians will not stay libertarians. They can't become libertarian permanently if it is only because of libertarianism's fashionable nature (which is it becoming fashionable on campuses), popularity (it is gaining), momentum (which we have), etc. You can't pretend to be a libertarian, for example, to get a girl, and then think that's sufficient to be one for life. You have to delve into the ideas, and eventually wade into the deep end of the intellectual pool to temper your own ideas. This is done by not hiding radical ideas, but effectively arguing them down (you can't say you swam in the Knowledge Pool just by dipping your toes in the shallow end). If you can do this to the person's satisfaction, then they will be a minarchist, but dedicated to the cause we all share (until we get to a minimalist state anyways)...or they may, in minority, take those radical ideas as better arguments, more logical and thereby ethical, and become anarchists. Either way, they aren't going to become a libertarian
that way...only to vote for neocons and progressives a few election cycles later.
Intolerance is not a calling out of bad ideas (no matter how uncomfortable it makes you). Intolerance is exclusion. And even if you see "purists" (some, not all, as you said, OP) as "intolerant", if their "intolerance" for non-purist ideas doesn't result in coercion, who in their right mind as a libertarian would give a shit?
Long story, short: Minarchists calling anarchists intolerant seems to me to be the pot calling the kettle black.
... because the attitude of more-libertarian/correct-than-though can do dis-prorportionate harm to our achieving ends that we pretty much all agree about. 
