Er, I don't think he was trying to be insulting, but his manner can be a bit flippant sometimes. In this case, insensitive, maybe but hardly to the level of "discrimination" that requires a "public apology." Please......that's being over sensitive and you have neither legal nor moral grounds to claim it. You want REAL discrimination, you go to Cathay and watch them serve particular clientele over locals regardless of who came in first. Otherwise, just vote with your feet as you've already done.
If you're going to be this sensitive, I guarantee you that somewhere along the way, you're going to be pissed with every major camera shop that's discussed in these forums. Just read the forums, and you'll see that everyone has a kudos to give or a horror story to tell about their "favourite" camera shop. And this hardly constitutes the worst of the transgressions: heck, even in case of attitude, this is open to interpretation at best, and doesn't compare remotely to anything else you read on the forums.
I don't think you've considered the fact that he may have made that remark in the light of the fact that nobody in his customer base buys 52mm filters, and that also explains his lack of stock for it? In which case, the remark is not directed at you but at the scarcity of requests for that filter. You make a vain attempt to turn it into a matter of class discrimination by saying he is discriminating against those with kit lenses: how the hell would he know what you were shooting with? Some very expensive older Nikon manual lenses use the 52mm filter size too: if he had made that remark to them, what would your spin have been then?
John 3:16 has much in their act to clean up, I agree. The LONG waits from asking for a lens to paying for it, are why I don't go there anymore. I know exactly what I want, so these days I just go to Lords or Orient Photo, no fuss no muss shopping. Your mileage may vary.