I'm not keenly familiar with the details but the customer's complaints seem to contradict the fired employee's versions significantly.
In business, in general, you want your employees to be pleasant, even when handling customers presenting a problem. if the customers weren't swearing, and otherwise offending other patrons, then the staff should have been very polite, and the customers should have never felt an adversarial presence. The employee should have generally kissed ass to get them to yield to the rules. How you treat customers is the difference between failure and extreme success. Every customer is a potential fortune in directing new customers to your establishment. Instead of saying "Hey no rags!" or "hey you cant' come in here wearing that" The customer should have been told something like "Excuse me, personally I really like your head gear, it's really cool, it really is nice looking, but I wonder if you wouldn't mind taking it off? don't get me wrong, it's nice and it would look great if you kept it on, but then the other people who wear gang head gear will cause us problems if we don't ask all of our patrons to remove their headgear as an equal and fair rule, so could you help us out and remove it while you're here? we'd really appreciate it and we're sorry if it inconveniences you, but we hope you can understand why we're asking? it's not so much about you, as it is others who actually cause problems".
In this day and age so many businesses have forgotten the concept of the customer is always right.. and while the owner might have douche tendencies lol (i dont' know, maybe not) I'm inclined to side with him at least initially until more data comes out.