I used to lead and attend a lot more club rides but cut down the number precisely because of behavior you describe. Of note, there was one fairly regular guy who would block cars just for the hell of it. One year, during our club ride to Brooklyn, he started to ride across the footpath of a bridge where you were required to walk your bike. He nearly got a ticket from the bridge troll. He would do stuff like that because he had some chip on his shoulder. I was so happy when he moved away.
The way I dealt with bad behavior on my rides was to say things to people and make sure they knew I was serious. Between that, being a sticker for starting on time, and the fact that I lead rides that require some travel, I only get small turnouts of people who, for the most part, don't do stupid s**t. My reputation precedes me, and I am happy for that.
As for bad behavior on rides led by others, there are many rides I simply will not go on because they are too large and the leaders only pay lip service to proper, safe and courteous riding. Indeed, some of the leaders of such rides can be the worst offenders.
The whole thing is really a damn shame.