At the same time, anyone who wants to counter protest to declare that the other person's opinion is not shared should be allowed too. And the original group should be grown up enough to allow other people their right to free speech and free assembly as well.
Getting shouted down is still allowing you to speak. Having an opinions means that other people may have a different opinion.
You can't respond to counter protests with violence. But that pattern of physical bullying was well laid out in dumps campaign. Happened a few times, and other than a few words, was never really stopped. I thought it was more encouraged.
BTW, I do remember that Brent was very, very upset at the protests in Minneapolis, I don't recall any real threats- but that they should not be allowed to protest like they did. It would taking some digging, but I clearly remember that.