If his explanation is not satisfactory, you may have some discrimination here, but I don't think it's practical to go to court given the costs. Cases like this typically settle. Given the situation as you described, even if you get a settlement, it may not even cover your lawyer's fees.
I'm not suggesting that you should suck it up. You can, for example, demand an apology. You can also complain to the Better Business Bureau. If you feel you've been mistreated, make it known to him and to others. It would be bad publicity for his business and he would want to avoid it (especially in CA, where there are so many minorities).
Whether he told the technician to make you wait would be a debatable point now, but he should at least give you an explanation as to why he chose to work on the other late customer first and why he let the technician move on to other cars when he know (or should have known) that you had a work order. Once you get the explanations or the lack thereof, you can start from there.