I doubt JWs care to mention what religion they're affiliated with at the door (I've heard this more than a few times - word is out re/the cult) so doors won't be slammed immediately, and they aren't going to blow a potential study/convert revealing the daughter's possible interest in the religion. I don't like the JW's aggressive behavior re/the mother's phone but he could be upset/angry in the event the daughter lied and put him in this negative situation and now he's dealing with a big issue. Regardless - he's the adult and she is just a young girl -- he could have used self control and conducted himself in a cultured way or just lost it if the mother was accusational, crazy/whatever.
I commend the parents being protective of their daughter especially if aware of the WT cult. They've hurt/scarred too many innocent people and haven't cared a bit about the victims or their welfare.