If you pulled out criminal trespass (legit reason), how many folks would you have to call the cops on (per day)? Each person that came in and asked to use toilet, without buying a cup of coffee?
If anything, the lesson learned here is to shut down all public toilets, and make folks pay a buck each time (like they do in Europe now at train stations).
Don’t be stupid about this. Asking to use facilities is fine.
It’s the refusal to leave when told to, to the point of defying a justified personalized police order to do so and requiring ARREST to compel removal from premises.
If anything, the lesson learned here is to (A) be a customer when facilities are for “customers only”, and (B) GTFO when police tell you to vacate private property.