Serve
Whenever I hear about a restaurant or other establishment that refuses to serve police officers, I always want to ask, “Do you expect them to serve you?” After all, their service requires them to (at least potentially) put their very lives on the line for you. The worst that can happen to you by serving them is getting a rotten tip.
It just seems reasonable. When people put themselves out for you, you should be inclined to do the same for them.