Anger in Politics

The first thing I'll say is that it definitely seems as if it's gone too far. There really seems to be no middle ground.
What I don't get are the Democrats who "can't believe" the conservative Right would use rhetoric like "Hitler" and "Fascist" and "Socialism."
Politics has always been divisive. But it was in fact the Democrats who took it to a whole new level during the Bush Administration. As a matter of fact, these were the first times the "Fascist" and "Hitler" terms started being tossed around.
They mocked his speeches. They booed at the State of the Union. They sang "nana nana, hey hey, goodbye" at the Obama inauguration.
So while of course it doesn't make it right to do, isn't it the Democrats that took classlessness to a whole new level in politics, and Republicans are just giving it back? The Democrats created the current political climate that they're suddenly shocked by.