I watched a video today where a fairly based lawyer was discussing that you have implied permission to enter a store open to the public, but a store can also put whatever conditions it wants to modify it (ie No Guns, No Backpacks, etc).

The lawyer essentially argued that the act of trespassing begins as soon as you enter the store and knowingly break any of these arbitrary but posted conditions, even if no employees directly confront you or ask you to leave.

So I suppose if the Pet Store had an explicitly posted "Code of Conduct" (ie We don't tolerate any verbal abuse of our employees, etc), a customer would be under obligation to leave the premise if breaking the code even if the employee asking them to leave didn't have the direct authority to do so.