Regardless of how you feel about his politics, Rush is a con man and a hypocrite. While he can pick apart the logical fallicies in arguments for positions he does not agree with, he will use those same logical fallicies to advance his own arguments. One does not have to listen to him for long to find examples.
Once I heard him arguing in defense of a student who had been suspended for being drunk and shouting epithets about blacks, gays, and feminists outside some dorms at 2 AM. The university said he was suspended for being drunk and disorderly. Rush felt that it was because of the things he said (and I agree). To "prove" his point Rush said (paraphrasing), "Consider a hypothetical case where he had been shouting epithets about white males. He wouldn't have been suspended, which proves my point." That this doesn't prove his case is not my point. The next day a gentleman called in to argue some point with Rush. When the caller said "Consider the hypothetical case where..." Rush cut him off and said (not paraphrasing), "We don't deal with hypotheticals on this program."
When Congress was debating whether to impeach Clinton there were many opinion polls that showed that the public did not support impeachment. Rush stated that these polls were irrelevant, that this was a legal case and all that all that mattered was the law and whether Clinton was in fact guilty. But a few weeks later, when the Microsoft antitrust case was in the news, Rush, who sided with Microsoft, touted opinion polls that showed that the public supported Microsoft. Apparently the law wasn't as important in that case...