In the name of "promoting bicycling" they do things as mentioned in the second article you linked to...Such as riding against red lights, thereby blocking the flow of traffic through downtown $CITY at 5:30 pm on Friday. This has the effect of severely PISSING OFF MOTORISTS who are TRYING TO GET HOME.
I've been to one CM ride a few years back when I was cycling heavily. I heard people walking up Michigan Avenue alongside us asking some riders "What's with all the bikes?" The sole reply was "Critical Mass"...As if that were supposed to explain everything.
After riding about 2 miles, I'd been through enough red lights and seen enough pissed off pedestrians and motorists to know that I wasn't quite so activist in my cycling. I was there for a ride, not to get people angry at me...So I stopped riding. Never again for me.