I keep seeing people talk about how the groper is going to react... seriously, who gives a shit how the villain acts, he's the fucking villain in the situation. You may as well point out that a rapist isn't going to react well to being made to stop raping someone; I'm stunned you'd even think this a valid point to make.
When people act inappropriately, it's doesn't matter what they think or how they react; they're in the wrong, their feeling are irrelevant. Concern yourself with how the victim feels and stop sympathizing with the groper.
Look back at the story of the woman who stood up for her feelings at the tech conference by calling out behavior she thought was inappropriate. Some people agreed with her, but others derided and attacked her.
Whether one side or the other was more morally correct in your eyes is not the point. The point is that it sucks to be the object of social tension.
And it's not really fair for you to define how tolerant other people should be of that pressure.
It's hard to do any of that when 5 minutes in, you're shoving somebody and chastising them publicly.
The groper is not going to react well to that. They're not going to think they did anything wrong (if they did, they wouldn't have done it in the first place). So they'll see her as the aggressor and complain loudly.