I think the OP's question is a different issue than someone telling you what to do on a group ride. I've never experienced that, but I only ride with a group that wouldn't do that... and they are not training rides. I've instructed people when I am leading a ride (i.e. drop down a gear, spin, try moving back on the saddle), but that is part of my job. I've had a couple of people on our rides (always men) get pissed when I tell them some kind of safety instruction, like please move right, single file, a car is coming.
As far as the yelling at those breaking the law.. well, I do it. Not all of the time, but when it looks like someone's in danger, or on the very rare occasion I am on a bike path. Mostly they give you a dumb stare, not really angry, just like, "what the hell are you talking about?" A few years ago, when I lived in a different town, DH and I were coming home from a ride. We were on the street that our development was off of. It would be classified as a country road, narrow and windy, but fairly busy. Suburban-rural. Anyway, we came upon our neighbor, who was riding with his 2 kids. The kids had helmets on, and were riding on the right side of the road. He had no helmet on and was riding against the traffic. I yelled out, "Jim, you need to set a good example... wear a helmet and ride with the traffic." He listened, because next time, he had a helmet on. And although this guy went to Yale, he didn't exactly have good judgement, as he had a couple of DUIs. Safety was not a concern.
Truthfully, I remember riding the wrong way down Rural Rd. in Tempe in the 1980s. Then one day, I had a funky incident with a car at an intersection and I realized the error of my ways. But, that's what I was taught as a kid, so who knew? I would not have been mad if another cyclist had told me.