My take on this is that a situation like this can turn on you if handled badly. You stated it is a social setting. Have you confided the discomfort of the situation to other girl friends? We naturally protect each other as the strength is in the herd. You may want to stay in the middle of the herd. A simple, "why do you keep pawing on her, can't you see she doesn't like it?" will sometimes do more than trying to settle it alone. When I encounter that sort of thing I always try to be a lady first. Evasion is my first tactic, I look with the eyes in the back of my head and seldom sit in a way people can come up behind me. Also girl friends can alert you he is swooping in. Many disapproving female eyes will shut down most men. If that does nothing your creep meter should be pegged. A discreet conversation with your local PD may be in order too. Formal charges or a restraining order can also initiate a dangerous clandestine vendetta from him. They can just keep a watchful eye and it is proof you are the victim, not the instigator. From there, watch him and your own behavior, what does it look like to others. That's sad but maybe fact.
Here is a scenario of it turning on me. Regardless of what I do, I am a potential target. Let say God forbid, I am arrested for any reason in an altercation of trying to physically protect myself. If I make a huge inappropriate scene, I have just been culled from the heard. If it goes to the courthouse docket, I am sitting in the same row as others of petty offences. As the news media is scanning for juicy mud and ratings, they scan the line. They pass over all others as nothing they can use. Oh boy! We have a headline. PERVERT TRANS SEXUAL ATTACKS UPSTANDING CITIZEN, FLEES TO LADIES ROOM AND HOLDS CHILDREN CAPTIVE! NASTY PERPETRATOR BROUGHT TO JUSTICE TODAY! Don't doubt that is could never go just that overboard. They would have their sensational headlines, then my life becomes a circus and they don't care the damage done to me or my children. I am an expendable non-human in their eyes, so they care little if it would ruin me. The burden of proof may be on the accuser, except the news media and also smears of public opinion. Tell me I'm wrong?
Please tread carefully. Touching an man in the groin, any contact there of any kind, not matter how well deserved, instantly brands you the pervert. After all, they all know that is your true underlying motive, to get to men's crotches. Don't let our societies sickness harm you. Don't ever open that door. Hug. Joann