I think he was talking in general as a person, not as a therapist. Like, small children are fine with him as long as they are not being disruptive. Non-parents who haven't spent much time around children often find babies and young children crying to be stressful and perplexing because a) it's unpleasant to listen to (also true for parents!) and b) it sometimes it means something is wrong and they have no idea what to do.

I also think crying in children and crying in adults are related phenomena but really different. Babies cry as their main form of communication and it can mean literally anything. Adults (especially in therapy) cry because they are upset and in emotional pain and they are able to talk about what they are feeling. His feelings toward the latter situation are likely to be quite different.