I believe the Illuminati exists, but not in the way everyone perceives it; controlling the media etc.
They're probably just another fraternity group, like the Freemasons, and by being so secretive people like to pin the blame on them.
It's similar to when you were a child in a dark room; you are afraid of what you can't see, and you imagine all sorts off horrible and scary things lurking in the darkness waiting.
Because you have no knowledge of whats going on in the darkness, anything you hear will be a product of the monster hiding in the dark.
Either way, I don't think they are responsible for the death of Tupac (Or 9/11), the reason he was killed was most probably because of the East coast / west coast feud.
They openly made songs slandering each other, in one of his songs he even talks about how he had sex with Biggies wife, and as you know, all humans have breaking points, which is why I believe someone from the East just had enough of being slagged off and ordered someone to shoot him.
As for people who are dismissing other peoples religions as being stupid, it's their choice in what they want to believe, openly insulting a religion is just going to cause tension between yourself and the subject, and is certainly not going to make them change their mind.
Which is my next point, why do you want to change their minds?
If they want to believe in a religion, let them get on with it, the majority of all religious people are harmless, only a small minority are extremists, and everyone religion / group has extremists.
For example, The KKK are (supposedly) Christians, I'm sure as hell they do not represent the entire of the religion, the same goes for Muslim extremist groups such as Al Qaeda .
Another example of this, if an Atheist kills a man, it doesn't mean all Atheists are murderous.