Because why go for reasoned argument when you can throw around hyperbole?
Leftists are comparing Bush to Hitler. Bush and Bushites are comparing Bin Laden to Hitler. Apparently analogies are no longer rhetorical tools, but have become arguments themselves.
One of my favorite law professors used to note, humorously, that whichever side invokes Hitler first, loses. His point was clear: guilt by association always has been, and always will be, a logical fallacy. I don't know or care who started it here. So I'm going to call it: when people on both sides stop arguing and resort to yelling and name-calling, we've all lost.
Dammit. I hate losing.