There is a simpler solution.
Yes you have to serve them, but the quality of goods served cannot be enforced.
It is entirely possible to bake a flavorless cake just as it is possible to serve drinks that look like one thing and taste quite like another.
There is no rule that says you have to deliver quality goods. None whatsoever.
Actually, it can. If the service provided to the perverts is of significantly lower quality than that accorded other patrons, it is prima facie evidence of discrimination. Result: lawsuit. So you can't save yourself that way.
You can't even "discourage" them by turning a blind eye if the other patrons take matters into their own hands. As an owner of a public establishment, you are liable to some degree for the behavior of your clientele. Your customers drag these pervs into the alley and treat them to a blanket party. Result: lawsuit. You created and allowed a situation that failed to provide the basic protections due the patron of a public accommodation.
However, if one of your patrons were to "pick up" one of the poofs and invite them over to their place for a party, and a group of other thugs just happened to be waiting down the street ... Then you're pretty well off the hook.