Oh sure, it's totally ok. After all, if you are paying her then you then she has totally abrogated any privacy or expectation of respect that a normal human would have. In fact, if you are paying an escort to be with you in public, she should have no objection if you whip it out in the middle of a restaurant and tell her to drop to her knees. I can't imagine why any escort would have an issue with this - it's not like they are real women right?
I mean seriously - if you are having dinner with an escort, why wouldn't it be the same as having dinner with any other woman? If my date has been grabbing my crotch all night, it is probably ok, but if she hasn't been touching my ass in public, I wouldn't touch her ass in public. I don't see how that is a white Knight as much as it is basic courtesy.