Normally this might be 'normal' behavior among close friends, even at 30. But when several people team up on one person to really 'humiliate' that person inside the context of that game, they better be sensitive about it that it isn't bulling.

You really can only do that on one of the 'stronger' people in that group. Not the person everyone recognizes is bad at nowfights and has mental health problems(?, you are here for a reason I guess).

One would imagine they would be conciliatory towards you immediately after the snowfight, making sure that you know they were forced to be that mean for the sake of the snowfight.

I guess it all depends on context. It is also not clear from your post if you made it clear that in your eyes, they were crossing a border.

I don't know why people are so hasty in telling you to 'get new friends'. Maybe they are right. I don't know. These literal words can describe snowfights with a completely different vibe to them.