His question made perfect sense. Truthers and white supremacists are similar in that they both hold views that are not "mainstream".
You seem to want to claim that truthers have a right or duty to shout their inside job theories and slogans whenever, and wherever the mood strikes them. The question is, do you extend that same liberty to other fringey groups like white separatists? Are you prepared to welcome guys in KKK sheet outfits to a CFL rally? Can you comprehend how expression of those divergent views might alienate people who would otherwise support a movement for liberty?
I know speaking for myself, when I was at a Paul rally, and some fucktard started shouting "9/11 was an inside job", I couldn't decide whether to punch the asshole in the face, or just leave the area as quickly as possible. In the end I did neither, but the experience definitely tainted my perception of the rally, and of Paul's supporters.
Apparently, you care more about shouting stupid slogans than being politically effective, which is your right. But it's also selfish and shortsighted.