Violent mob or grandmothers pushing strollers?

Depends on who they're protesting. [Link]

So, in the case of a leftist protest, the protesters are depicted sympathetically, the reporter striving to stress their diversity and normalness so that any reader can see himself or herself in the protests.
And there is no hint of disrespect for the fact that yes, at some point, an email alert went out and people were told where to assemble.
On the other hand, when Obama opponents assemble (and that includes Democrats in good standing), the press strives to paint the protesters as not only weird and possibly dangerous ("carrying swastikas") but also deceptive, in that they're somehow "faking" their anger, or have been paid to be there.
Well, to be fair, some people are in fact paid to be at these protests. Some people belong to a hierarchical organization and are, in fact, part-time paid profession protesters, trouble-makers, and intimidators. Some people know exactly what to do and what to yell and who to push, because they do it every three or four months and it is, effectively, part of their job description.
But these people -- these people -- the media "forgets" to mention.

SEIU & Castor organize a townhall and announce it at the last minute as to reduce opposition voices. The townhall was packed 1/2 w SEIU people. When supporters of healthcare freedom (ie, anti-BigGovHealth demonstrators) were prevented access to the townhall they began to shout, bang windows & doors.