What about if you have a boy age 8 who tests out going to the bathroom by himself and some guy in butt chaps, no shirt and a cowboy hat comes in after him? Same reaction? What if this guy in your photo goes into the men's room and your 8 year is old is in there by himself?
Again, the better reaction is you leave, not them (same with the game, bench your player and forfeit, taking the consequences as necessary). And the simple societal solution is one which the Newsom bill put in a more positive direction. Single stall ballrooms should be gender neutral. Businesses, venues, government buildings, parks, schools and transportation hubs should offer more single stall options (both for the sake of the trans parents, and parents worried about small children)...new builds should require them (same as we did with handicapped stalls). If you have those options, a penis/no penis rule would be ideal, but you don't get to decide to violate existing law by going all vigilante on the trans person.