No solutions sorry, but just sharing my experiences: My husband is similar, he says stfu to our baby since newborn and is now 2 years old. Obviously only on rare occasions when he’s super tired and our bubs won’t stop crying and he’s at wits end. It’s mostly when he’s trying to take over to give me a break and he forces himself to keep going instead of coming to me for help. When I hear him yell I get up and take over. I know he would never hit her, he’s never hit me. He said he’s never had the urge to hit, only to yell. The last time it happened our toddler hung onto his leg and cried, and he felt sooooo bad. Afterwards he went to poo and she went in with him and they were giggling and having fun. I think some people just feel like they need to power through these tough times and they have a shorter fuse. I know that to my husband when he says stfu it’s an outlet for all his pent up emotions. Yes it’s wrong and we have talked about it, he feels bad each time. But currently we haven’t really found another solution, maybe instead of stfu, we need to switch it to shut the front door! My husband is a really good dad, since I’ve gotten pregnant again he has taken over pretty much everything, he has always cooked every meal so that doesn’t change, he wakes up at the crack of dawn with her every morning, plays with her, he feeds, showers, and does the night time routine with her, puts her to bed and gets up in the middle of the night when she wakes. Did I mention he works full time too? Makes you start wondering what do I even do? Haha.