I don't believe in "Illuminati"
Now it's ok if someone believes that it represents something.
Also ok if he discusses those things with similar minded community.
And also ok if he talks with other willing listeners about it who aren't aware of those.
But as soon as he gets obsessed with it. And starts forbidding and barring people from things that he deems as "Illuminati" -- then we have a problem.
This brings up an interesting question : Shouldn't we all be forbidding evil, taking it as our duty?
The plain answer is : for gray zoned things, its better that you follow what you believe in, without actually forbidding others based on your believe.