Your neighbors may shit in their pool. They may not even be aware that they’re doing it. They might think shit is just a natural consequence of having a pool. They may hop the fence at night and shit in your pool, oblivious as they are to the difference between shit and not-shit. That doesn’t mean you give up and start shitting in your pool, too. You clean it up (even though it’s not your mess) and you go back to enjoying swimming in a nice sanitary place where poops don’t hit you in the face when you come up from underwater. You invite your friends over, because swimming in a nice clean pool is more fun for everyone, and it’s more fun for you if you’re not swimming alone. As a result, if your friends decide to dig pools in their backyards, they know shit and pools are not irrevocably linked and they work to keep theirs clean. Slowly, you all hope, everyone will see how much nicer that makes swimming.
If you can read this, thank a teacher.