In your post, by "they" you mean left-wing whackos, people on blogs, and those far outside the mainstream political spectrum. What we've seen for the last 2 years is that the crazy rhetoric, usually reserved for the far right wing of the Republican party....has come from the congress-persons and mainstream political figures(i.e. a Sarah Palin). In other words, the mainstream of the party. That's the difference.
...and guess what? Regarding Bush, you actually have an argument that he was a war criminal who shredded the Constitution(meaning you can backup your argument with factual analysis)...as opposed to baseless accusations that Obama is a M u s l i m, or a socialist/communist...coming from the mainstream Republicans. The gun metaphors and violent rhetoric that have came back to light are downright scary.
I've really tried to keep an objective opinion on everything, but what we're seeing on the news isn't reality. It hasn't been 50/50 on both sides, and nobody should be criticized for citing peoples' own statements and actions(and others should not play the victim, and make excuses for what they've done). Of course Palin, and the violent rhetoric we've seen and heard aren't directly responsible for this tragedy.......but that doesn't change that what he her, Angle, etc. have said/done is wrong.
Hopefully as a country we can have a discussion that will hopefully END this violent discourse once and for all.