I have no problem with anyone letting their kids stay up screaming at the pool until 12am, 1 am, 2 am, 3 am...whatever! However, before doing so, please provide me with your name and hotel room # so that I can drop my screaming cranky children off to you to babysit the next day.

Because when you keep my kids up at night, I don't necessarily want to have to deal with them being cranky, when I know it isn't MY parenting skills that are lacking. Oh, and when you see me in a movie somewhere, and my kids are screaming, and behaving badly, and you are telling us to be quiet because you can't hear the movie, just remember that they are doing this BECAUSE YOU KEPT THEM AWAKE ALL NIGHT! It is not because I let them eat too much sugar (I don't), and it is not that I don't try to put them to bed at a reasonable hour (I do), and it is not that my kids are bad (they are not - they are quite good, well behaved and polite children). They are TIRED! I know, because I get that way myself when people are screaming at 1 am!
I don't think anyone minds people in the pool late - that doesn't seem to be the issue. The issue is NOISE LEVEL. While some do keep their kids up late at night, and I don't have a problem with that, I don't, because my kids need sleep. And while I do ask for a quiet room, that isn't always possible. And while it is your vacation, it is also my vacation. So a little mutual respect is always nice. Swim late, just don't scream and makes lots of noise. If you want to scream, go to the parks where I can't hear you!