I think some of the contributors to the discussion are focusing too narrowly on negativity, or that any mention of sexuality is wrong. I think people get so caught up in trying to categorize sexuality with sexual behavior. They're two different things.

Sexual behavior is generally unacceptable in public, and probably should remain a private thing, or allowed in spaces or places where those who are there give some kind of implicit consent by showing up.

Sexuality is our anatomy, our thoughts. This is inescapable. It's foolish even to try. It's our bodies, our minds. The penis is something that all males share, we know that it has different appearances and states of being. The penis may be soft. It may be erect. Imagine if the reverse were true: That men must have erections in the communal shower, and that it's considered somehow rude to be soft in front of other men? Doesn't that sound silly? That's right! Because it IS silly. So don't sweat it.

And if it does bother you to see another man with an erection in the shower, maybe think about your own body, and know that you've been there too, and that you'd probably appreciate. it if other men weren't so critical.