AD, the things you speak about... horse play... initiations... hazing... what ever one calls it, is very common in athletic sports such as football, hockey, curling... wait... no, not curling... lol...
Because it's always been done, or done within specific groups, whatever... the group generally determines what is "right" and what is "wrong" as far as display and activities such as those.
That you don't like it is the important part. Does that make you a prude? Should you condone it? Or turn a blind eye? Those are tough choices.
Frat houses get shut down and sports teams investigated over these types of allegations made public.
My best guess is not that you think there is anything that is dangerous or harmful to your sons. Rather, it makes you uncomfortable.
I agree that type of stuff is just... bizarre and childish... In some instances, it could be a swat on the rump by team mates of a football team... or towel (or other method of) snaps to the groins... or it could be communal showering...
Is it intended to be a power play? An alpha, dominance thing? Abusing, humiliating, shaming them into submission?
Of course, them understanding that they do not have to accept nor participate in that type of behaviour is important. They may not say it openly in front of their friends or their dad, but they might say it to you, in private, and they should know they do not have to participate in that behaviour.
