As someone who knows some Fortnite-playing kids, I'll say that even if it isn't creating murderers, it is teaching obnoxious behaviors like those taunt-dances and (offline) playing pretend-war in the faces of people who aren't interested.
An avid Fortine-playing 9 yr-old tends to be more annoying in person than a 2-D sidescroller player or even a Minecraft player.
I don't agree though with the part that the game is not bad.. fornite was no accident at all anyone who thinks that may not understand the cost of developing a products like that. they are deliveridly targeting people that easyly get addicted.
this is the same argument made with lootboxes.
note saying the game is not to be blame, is not an excuse to bad parenting, is just that the makers also have a bit of responsibility when they exploiting a known social behavior for cash.
What is specific to gaming is social approval by culture. When you go to most sport club or hobby club, eventually adults stop that crap or voice disapproval. Not in every club and adults do swear etc. But, in the straight assholery tend to eventually be criticized and talked about.
Gaming culture does not really do that.