I did address it. More than once.

I know that sometimes it’s hard to control laughter and laughter is a very common reaction to being nervous or anxious or embarrassed or being put on a spot.

Also I don’t understand what you mean by “shouldn’t hold back laughter”. That’s exactly what he should be doing: trying to hold it back. You wouldn’t want him loudly laugh with his mouth open. He had a reaction so he was trying to hold it back