Media Treatment of Leftist Protesters Versus Tea Party Protesters

Good stuff from Tigerhawk:

Glenn Reynolds makes an excellent point about the highly variable twisting of media hankies over "violence" at demonstrations. A few clowns shout at a "tea party" and the media starts worrying about the resurgent Klan, but the left literally attacks the police at the G20 protests and nobody says anything.

There are two possible explanations for this different approach of the media to edgy demonstrators of the left and right.

First, the mainstream media are completely in the tank for the Democrats, and want to help them push the talking point that the tea-partiers are both extremists and typical Republicans (neither of which is generally true).

Second, the left benefits from the soft bigotry of low expectations: People expect leftists to act like thugs at these gatherings as they have for 40 years, so when they do again it is the same-old same-old. The striving burghers of the right, however, have never done this before, so it is news.

Both explanations are probably true to some degree, but which one dominates?