I too have been going to anti-war rallies since I was in single digits. I have never seen a poster of Bush (I or II, or Nixon, or Reagan) as Hitler or anything akin to the Joker. Yes, I saw plenty of chimps, and lots of "some village in Texas is missing an idiot" type stuff, but never caricatures as Hitler. I Googled, and found such caricatures on Iranian and Saudi television, but not at any peace marches. And as Joyce points out, I sure as hell never saw anyone with a rifle.
I think there is a difference in kind, not just degree between the protests under Bush, and those under Obama.