I'm not even that close to my mom and I would literally kill anyone who dares to call her a "whore". It's not that I agree with what the kid did, but I understand why he did it.
Yeah sure, momma's boy.
I have parents who say extremely awful stuff about other people I know and care about and spread that information around. These people won't stop unless:
1. You can win verbally (mess with them emotionally with words) and defame them of their precious friends and make them lose their minds before you do.
2. You switch from verbal to something more.
You can't expect such a young kid to win in a verbal fight where the grandparents have an authority advantage (controlling his environment, including survival essentials). I really doubt this kid acted on a single comment, like some bad-ass wannabes think he is ("OMG, if someone calls my mother a whore ONCE I will LITERALLY kill them"), but rather a continuous unwanted dose of hate spreading.
The kid didn't act normal, but normal grandparents don't call the mother of their grandchild a whore either. That's no different than being called a
bastard directly. While I don't think they deserve death, I have no sympathy for those dead folks.