Wristslapper

Someone who either acts or is genuinely so stupid that they incite rage in everyone that interacts with them.

Can also apply to the kind of people who think that 'your mum' is a valid point to make when losing an argument.

A: "I was speaking to him the other day. I say 'speaking'... I had to walk away in despair after about two minutes."
B: "Yeah, he is a bit of a wristslapper."

A "I'm not insulting you. I'm simply saying that your opinion is based on something that isn't true."
B: "Your Mum."