With all due respect, I hope your husband realizes that most people, definitely including myself, don’t know the proper way to respond to someone in such a situation. Awkward responses are likely to be ignorance, not malice.
Perhaps you can can help. Is it better to ignore the obvious? Ask about it?
It’s better to ignore the obvious until you get to know the person well enough to ask- usually by then it will have come up in conversation anyway. Hubby doesn’t even mind if strangers ask, as long as they don’t do it in a rude way. I have no problem with people being uncomfortable from not knowing how to act and neither does he- but there is no excuse to be rude as some people really are. Some people forget a person with a disability of any kind is a person first- just address the person not the disability.