[TurtleSoup]

People seem to think that a son/mother relationship is always the same.
I'm willing to bet his mother has the same humour, she probably calls him a wanker affectionately, some people can't express affection by hugging and being gentle, they express it with jest or insult.

It's like if someone spends lots of money on you, you might say "Oh, you idiot, you shouldn't have"
That's not disrespectful!