Mark, I'm sorry that you've encountered prejudice and ignorance, the world seems full of it on many levels. Sometimes because people are cruel, more often because they are just downright ignorant, result is still the same. I think there are also people who mean well with a comment, however a poor choice of phrase, timing or judgement let them down and it comes across poorly.
On a flip side, I was put into a slightly awkward situation by a customer some time ago. He was present whilst working upon his sportscar, as he was interested in what I was doing - no problem. He is a very intelligent man, a PhD holder in the subject of languages and a lecturer at university, and a very interesting chap to talk to. To my mind irrelevant, he also has suffered from Spina Bifida from birth, and is confined to a wheelchair. We were chatting about this and that as I worked, and then he announced late afternoon that I was 'obviously uncomfortable with his disability'. I was a little unsure of how to respond to this, he explained that he felt there was an atmosphere because I'd not asked him about being a wheelchair user AND owner of a sportscar, etc etc. To be honest I was a little offended, and said that I had no real opinion on the subject, and saw him as a customer who enjoyed cars like me and many others. I felt no more need to comment on his mobility than I did a wearer of spectacles on their vision shortfall, etc. It was really uncomfortable after that and he said he felt I'd been rude by 'ignoring the obvious'. Sometimes, you just can't win.