My husband stutters and his bio mom was/is awful about it. I refuse to spend time with her at this point (he still tries to have a relationship with her), but I’ve seen her interrupt him, roll her eyes when he’s talking, insult him, mock him, all of it. He lives with her until he was in his early teens. He ended up with amazing foster parents who are so accepting and supportive, so that helped a lot. I can’t imagine him not having had them and just having nothing but his mom’s negativity and criticism.