Sounds like homosexuals partying. I suppose it could be hetero men behaving badly, but I doubt if hetero men would want to wear mankinis to party — definitely sounds like queers to me.
So, "stag party" has lost its rich historical meaning... bachelors whooping it up with strippers and excessive liquor the night before the wedding... and has been redefined as a gay male sex party.
What has the world come to?