Nah, it's actually about the hyper that makes violent comments okay. Hyperboles are usually used to make something apparent, in this case what's being made apparent is the irony.

For example: "Hey, can I go to the party?" "No" hard to interpret if it's a joke "No fucking way dude, if I see you there I'll fucking raze your household to the ground for 4 generations" < this is such an exaggeration that is simply can't be true, which in turn implies that yeah, they can come.

Of course, for it to be effective that must sound completely impossible to the listener, and as always context is important. Of the context of my hyper violent message is that I'm talking to my friends, they will know I'm joking.