kids commenting on peoples apperance

Hello,

We live in Israel and today were in the elevator together with a man of
(presumably) Ethiopian descent. My 6 year old son said to him "Your
ancestors were from Africa" . The man was really nice and said "That's
right, where are you from?" and my son launched into a discussion of
the many countries in which he has lived.

In the past (about 2 years ago) my son went through a very short phase
of commenting more directly about peoples apperance (e.g. why does that
man sit in a wheelchair, why does that man have dark skin). I explained
that it was impolite and could make people feel self-conscious and he
could ask me such questions quietly in private and he soon stopped.

Do you think his comment today was inappropriate? Should I tell him
that it is not polite to make such comments? I'm not quite sure how to
respond to what happened or if I need to respond at all.

Thanks for your advice,
Helen