I think the take-away from this topic is that water isn't really the issue, it's the presence or absence of a bunch of junk in it.
While disposing of clean water is pretty much a victimless crime, dumping polluted water is horrible and we should all agree that it's the wrong thing to do. Dumping water with food waste, toothpaste, and detergents is wrong. It's littering and it's polluting.
If you just dump a little bit, you're only polluting a little bit, but you're still polluting. The part of your conscience that tells you to look both ways before you dump it is the part of your conscience that should actually be telling you not to dump it at all.
Pack it in, pack it out.