I think all critical mass groups are different. The CM rides in Knoxville are not very 'critical' in their mass as usually less than 30 people show up to ride but they have a pretty good relationship with the local police and overall I think they get more smiles and waves than honks and obscene hand gestures from passing motorists.
A lot of the problems with CM in cities like SanFran and NYC was that the authorities arrived at a bad situation and made it considerably worse by using excessive force and falsifying reports about what happened.
I'm neither for nor against critical mass but I would suggest that regardless of which side you take you should check out the documentary called "Still We Ride" about what happened that changed the fun/easygoing Critical Mass ride in NYC that was attended by all types of bike lovers into the protest ride comprised entirely of cycling extremists that it is today.
Available free on youtube in 4 parts:
Part 1►
YouTube - Still We Ride
Part 2►
YouTube - Still We Ride
Part 3►
YouTube - Still We Ride
Part 4►
YouTube - Still We Ride