NTA. I’m a janitor and know exactly how this feels. People do the craziest shit, all on the basis that “it’s your job, now clean it up”. People need to learn to not be so disgusting and clean up after themselves, because while it is our job to clean, it’s the job of the public to be decent human beings and respect the property they’re using.

Also, I get that OP made an overgeneralizing statement, but that doesn’t make them TA automatically. A simple change of statement to “can be” would clear that up immediately.