Paul's line about WWII was an error.
Here's the transcript of that portion:
Q: You sound like a proforma 1930's isolationist.
A: No, I'm not an isolationist - I'm a noninterventionist - because the founders of this country, that I listen to carefully, were very much - they were not protectionists at all. They were free traders, they wanted trade and travel and friendship-
Q: If fact that's your point. You say you're the true republican when it comes to the republican candidates.
A: Right, and Robert Taft is the example I use. He did not want to be in NATO. And there was a strong element in this country that didn't want to go with World War I and World War II. Even the president has advocated peace - we'll never take you to war in Europe. And I like that old saying. Don't go to war in Europe and don't go to war in the Middle East. It's best for Americans to stay at home, mind their own business, become a wealthy, prosperous country. Set a good example, and they'll want to emulate us. We can't force our ways on other people through the point of a gun.
=== end of interview ===
Most Americans believe that America won WWII and prevented Europe and Britain from falling to Nazi Germany. You simply cannot come anywhere close to implying that America should have stayed out of Europe in WWII.
In my opinion, Paul needs to be very careful here when discussing nonintervention. He is vulnerable on this point because Giuliani and McCain will draw parallels between Nazi Germany (Hitler), and Al Qaeda. They can effectively argue that the reasons America had to be involved in WWII are the same reasons America must have an active military throughout the World - and particularly the Middle East - to prevent the rise of evil.
On WWII, Paul simply needs to say that WWII was a just and Constitutional war. Congress made a formal declaration of War in that case, so America was right in fighting to defeat Nazi Germany. All American wars since have been unconstitutional because they are not debated by congress and are fought without a formal declaration of war, as required by the Constitution.
Never try to link the concept of nonintervention with WWII (my opinion.) The concept of nonintervention goes out the window once Congress declares war.