You can't discriminate.
You CAN discriminate --at least until now-- against certain behavior.
For example, a restaurant could rightfully eject a patron who smoked; or who insisted on spitting on the floor; or even who persisted in merely speaking so loudly he was disturbing other patrons.
Until recently, homosexual behavior was considered...a behavior. Now it's no longer a behavior, but a "protected minority" status.
What if two men walked into a motel and asked for a room with double beds?