Well, not citing anything specific, he tends to, as greg said, simply make things up. He will cite sources that are completely bullshit. He will make claims that are completely unfounded and just untrue. He does it blatantly in many cases. I will try to find some examples. I remember one having to do with cigarette companies. Some rant of his, he ended up citing some ridiculous study done by some weird contractor working for a cig company, and idk if the study actually even existed.
Not to mention he just went on the air and called Obama "uppity." And excuse my language, but uppity simply refers to the phrase "uppity ******s." Basically, Rush isn't a reporter or even a legitimate news commentator. He's just some dude who screams and says off the wall shit to get ignorant people rowdy. However, he sells his stuff as legitimate news and editorial.