The fact that they went there asking for the girl is no big deal. Obviously there's been some previous interaction. I see no issue with the mom questioning and videoing the guy who got cagey about the whole thing in a world where weird people sometimes do awful things to kids. She's just looking out for her daughter (and we don't know if there could be a reason for her to be antsy in particular) and the JW couldn't be a grown up and had to act weird which made it more curious. Him slapping at her was uncalled for.
Funny, JWs have no problem recording things in public but don't like being on the other side of it. You and I know the guy was just some dumb JW trying to get his time in but those on the outside don't. He handled that very poorly.