i used to belong to a gym where it was fairly common to see guys getting boners and even jerking off in the steam room or the sauna. sometimes it even went beyond that. of course, a lot of the guys who worked out there were gay, and most people either ignored the jerking off or just watched.
sometimes, i had to keep hold of my own junk to keep other guys from grabbing it and trying to jerk *me* off. there was even one guy there who tried to go down on me a few times. i had to push him off, cuz just saying no didn't seem to work.
my attitude to this was that some guys kinda treated the place like a sex club, and i didn't care and might even watch if it looked interesting. but i felt different if it was somebody coming on to me, cuz i didn't want to have sex in "public" (even if it was mostly a gay crowd). i admit sometimes i would pop a hardon cuz of what i was seeing, but i didn't want to make problems for some of the str8 guys around there.
once in a while, the gym would pull a member's card for "sexual activity," and i didn't want that either.
i'm the first to admit that usually i like to see guys jerk off and i like jerking with other guys, but i agree that it's much better when it's clearly consensual and no chance observer is gonna get sore about it.