A couple of observations:
Old Fart--I'm 44, I guess I missed your arbitrary cut-off of 45.
Boy, I can't wait to get my Jerk License.
Your admonition to me is misguided--I had the same experiences as you, and more. Again, it's got NOTHING to do with nudity per se.
Like other posters have discussed, not only have I done the group shower thing in school, also in college, in my 4 yrs in the military, while working a factory job in HS, while working at a large law firm, and even showering in the buff, in the wide open, in full view, while working on a farm.
The OP was talking not about normal conduct, but about LOSER conduct. It's not about nudity, it's about being an inconsiderate a-hole, or an outright perv.
Furthermore, about homophobia--the Y I go to is famed for being Gay Central. EVERYBODY I know there is gay.
This has absolutely ZERO to do with sexual preference. There are 2 kinds of people, whether gay or straight: considerate, civil people, and inconsiderate a-holes, including pervs.
I went to breakfast after a workout with some of my gay friends, and when they asked me why it took me so long to get to the restaurant, I told them that I went in to take a steam after working out.
They were totally grossed-out, and told me that not only do they NEVER go in the steam-room, but they try never to go anywhere near the upper locker room at all, because it was full of "disgusting creeps"!
And this is coming from some really promiscuous flamers. When I told them about the Y with the old naked guys sitting around watching TV on the vinyl sofas, they told me that nobody goes there UNLESS they are of that ilk, and that that Y had been infamous for such conduct since the '70's.
I guess in having chosen vinyl upholstery, the Y was expressing a preference for the spread of chlamydia over bedbugs.
Some people just have no class. When I was in swim lessons as a little kid, some other kid decided to pull a "joke", and do the piss-on-my-leg-in-the-shower thing.
I knocked out one of his two upper front teeth, and that was the end of that. The unexpected thing was that I became everybody's best friend, because he had pissed on everybody else, too, but nobody wanted to do anything about it.
Finally, my wife reports that women are EXTREMELY sensitive to nudity in the change room, and will go to great lengths to not appear naked, unless they feel that they are surrounded by their lifelong friends--and sometimes not even then. She says it's a body-image thing.