Is letting someone know that they hurt your feelings mature?

Or is it immature?
I just went off on a guy friend because I shared my concerns about my stepdaughters health problems and he couldn't get past me mentioning she has bowel dysfunctions that cause her to leak stool. What set me off: "no offense but I don't want to talk about some little girl pooping her pants that's nasty."
That little girl is a child that I love, and she's living in a complex social situation, depressed, and I'm worried for her and upset that I'm seeing her suffer, and I can't do anything about it. Long story.