Well, you would refuse to shower in a costume and claim you would change pools if this was a requirement.
Yes. If a pool didn't accommodate my preferences, I'd frequent one that did. Not go alongside people who were acting entirely within their rights and rules, and whinge that they were being 'inconsiderate' towards me.
That's not inflexibility, it's me taking responsibility for my own preferences and not attempting to force them on others. Something you could do well to learn.
Some people are exhibitionists. An absolute insistence on being nude in communal pool showers (especially when it has been pointed out this is offending the other customers as in the OP's example) does lead people to question why insist.
Well allow me to answer that question. Some of us, after swimming in water full of chlorine and urine, like to wash properly.
If you can't understand that this isn't sexual, and think that we are doing it because of YOU, that it is some sort of 'insistence', the problem is entirely yours.
And your problem is not my responsibility. You don't have to shower naked if you don't want to, and I don't have to waste time and stay dirty because you can't desexualise the act of showering.
Let me put it this way. You are, again, implying that I am a sexual deviant because I 'insist' on washing properly after immersing myself in human soup. You're entitled to be wrong, and prudish, and sex-obsessed, but you're NOT entitled to try to make me change my perfectly normal behaviour because it offends you for no good reason.
Exercise some of your own 'consideration' and accept that my washing preferences are not sexual or about YOU.