Isn't it something that not only do you have to do your job as a CSR, but you are also a sounding board for people's ignorance/intolerance. Welcome to the wonderful world of CSR work eh? *sigh* Been there with you, and it's really hard some days.

One thing I could think to say to someone like that, and hopefully not get into trouble in saying it -

"I'm really sorry you had such a hard time dealing with that".

In fact, what I would mean by that is "It's your intolerance/ignorance that put you in that position" LOL I'll bet it would slide by most folks as you sounding concerned and validating