First of all I don't know of any business that says they don't want to serve police officers. Assuming what you say is even remotely true, because one is discrimination, the other is not. You can not discriminate against race, gender, sex or creed.
You can not say I don't what to sever black, gays, lesbians or chinese, but you can say I don't want to serve unaccompanied teenagers. Now if an officer is off duty he is no longer an "Officer", but you can not be a off duty gay, black, woman or lesbian! But actually there are clauses that say you can't refuse service or discriminate bases on what people do either. So I really like to see the link. And even if the owner, or clerk did that, he/she most likely will be fired or fined!
Diving Mullah