mhsjax -
Have your contacted your local authorities about the situation? If so, get others to contact them as well. There is no excuse for causing dangerous traffic conditions. Most cycling groups do not behave this way - I don't know of any that behave this way but I'm sure there are some out there...as you have witnessed.
I'm a cyclist and I sometimes ride in large groups. However, we follow the traffic laws. We mostly ride single file. Occassionally, two across if there are no cars around. If there are cars nearby, we stop at all lights and stop signs. We never cross a road as a group and make the motorists wait on us...unless it's a planned event with a traffic cop or similar holding the car traffic at bay. As others have said, we're typically afraid of motorists. I know I can't win against a motorist and I won't ever try to push my luck. There are times I have to ride close to the white line on the side of the road due to road hazzards (debris, gravel, glass, etc). However, I've never held up traffic for any reason.
As others have mentioned, there are many motorists that are quite supportive and very courteous when passing us. And, there are some, unfortunately, that are not. Our group has had trash thrown at us for NO REASON, causing a couple of our cyclists to crash into each other; we've had people spit at us and we've had an occasional car come right toward us and swerve at the last minute, barely missing us. I've never been hit by a car but others in the group have. In each of the accidents, it was the driver of the car that was at fault, not the cyclist.
I'm sorry you are having issues with this group of riders. Something needs to be done before there is a serious accident. But please, don't lump all cyclists with this group.