I'm not very tolerant of people with conspiracy theories?

You should be more understanding and realize that what is official stated is not always true. I do not believe in many conspiracy theories (only one I halfway support is 1985 NBA Draft), but I understand that what is stated is not the complete truth and that people are inherently dishonest.
References :

The best way to be more diplomatic may be to be a good listener, and say nothing at all as they rant their goofy ideas.

Conspiracy theories can be compelling, but I agree with the principal of Occam's razor: "All other things being equal, the simplest solution is the best." Conspiracy theories are usually to dang convoluted and crazy to feel reasonable or realistic. I still enjoy a good story, so I like listening to them.
References :
http://en.wikipedia.org/wiki/Occam's_Razor

i understand what you mean, it bothers me when people try to question everything just to bother other ppl, but you have to realize that everyone is different, dont focus on thier point of views, focus on thier personality and thier kindness,
you'll be fine once you get to know them.

im a very religous person and i have two close atheist friends, you never know what could happen.
References :

I agree, I think that conspiracy theorists are just in denial of the truth. I do believe we should question authorities because they can be wrong too but I think that conspiracy theorists take it way too far. I don't know if you will be able to meet them halfway because they already don't believe a lot of things people say.
References :

Your endeavor toward understanding catches me off guard by its rarity in this nation. I commend you for it. However, I can't shake the feeling that instead of being completely earnest, you are but a pawn in a vast conspiracy to in fact catch me off guard. Therefore I must rant about your liberal and/or ultra conservative motivations, thus effectively ending all possible avenues of conversation.
Good luck, I hope you fail.
References :
In other words, don't take anything in life too seriously.

Maybe learning about their conspiracy theory will help you be more understanding. Unless it's completely off the wall, you'll probably be able to see some kind of sense in what they're saying, or kind of understand why they believe in it. Even if for the most part you still think it's a crazy belief, there'll be something there that you can say "when you put it that way, it does kinda make sense" about.
References :