Sexual dicrimination
Banning nudists' erections is sexual discrimination, particularly aimed at men with small penises or growers. Women can be naked however they wish, legs apart for comfort an maybe with erect nipples and engorged labia. But a man with an erection is banned, no matter how discrete. This particularly discriminates against Growers, doomed only to show their manhood in its diminutive state - not its full potential size. even Shower males don't suffer this indignity. Their penis being almost as it would be when fully excited.
ladies have it made they can wear anything they want or how little they want, they can walk out in the street and turn heads if a guy does that he's in trouble and a guy with a little penis not only in trouble but will probably get laughed at. at a gym those with small penis will probably never get a second look.