Not sure how to handle this

So Joel came home for cub Scouts very upset. The said they we're sitting in a group and talking about what makes each kid their different. The Den leader asked our youngest what made him and his brother different.

Our boy said he is taller than me.

Another child calls out and he has down syndrome and he's retarted and walks funny

The other kids laughed and the Den mother ok kids let's not make him feel bad because he's different. He was born this way and God loves him

Joel was so outraged he got both the boys and left.

I have never seen him so upset or mad. Our oldest boy is so embarrassed and went to his room. And tiny tornado is crying.

Joel wants to go back there and say something but I don't think we should handle that way.

I don't know how to fix this