As someone who did clean it up this is semi true.Oddly enough a homeless person almost never makes a mess of a public restroom. They need that restroom and can't afford to be told "Don't come back."
It's the people who are afraid of them who usually make the nasty messes that a clerk having a bad day gets tagged with "You're it, go clean that up."
Homeless people who leave behind their used needles are why many places have coded locks on their doors
The people most likely to make a mess though we're the Karen's