Don't disagree about how he should have responded - however we don't know whether he was sick like his ream-mates.And if he'd gone back at Wan-Bissaka again and again, United may well have finished the game with 10 men. Being regularly flattened goes with the territory if you are a wide attacking player. Christiano Ronaldo had the shit kicked out of him continuously as an 18/19 year-old at United, back when refereeing was a lot more lax and defending a great deal cruder, and just kept getting back up and looking for more.
Calling players out is easy and not necessarily helpful.