In my view, there are two groups contributing to the efforts to intimidate those opposed to big government (and the big-government-loving Obama administration).
First, left-wing pundits have adopted a concerted strategy to (1) stigmatize dissenters; (2) convince those who might be sympathetic to their cause that the social costs are simply too high to agree with them openly; (3) convince the uninformed or those perpetually in "the center" that the dissenters are such disgusting people that their ideas shouldn't be taken seriously.
The second group propagating this junk -- albeit somewhat less deliberately -- is the MSM. Because most of its members' sympathies lie with the left, they are more willing and better able to distinguish the left-wing dangerous fringe crazies from just the plain left-wing fringe crazies (and, chances are, they have some relationship, even an attenuated one, with someone in the latter category). In contrast, most of those in the MSM are neither willing nor able to make such fine distinctions when it comes to the right.
Hence, demonstrations that, when staged by the left (like the anti-Iraq war protests) seem to the MSM like a refreshing expression of spontaneous democracy and moral outrage become frightening and threatening when (like the 9/12 rallies) they appear on the right.