Is this immature of my husband

My husband has been in a custody battle with his baby mama for a while. Well Friday he got full custody and went to her house to get his son with the custody agreement and did the DUMBEST thing! He went LIVE ok TIKTOK and was saying "For all you women saying babies need to be with their moms. Guess what? Kids don't stay babies that long and before you know it they don't need their moms anymore. Us father's are coming for you bitches!" And he's on LIVE showing him giving his baby mama the custody agreement and said "Read it and weep bitch!" And telling his son to get his stuff because he's in his custody now and he'll see his mom every other weekend. He's laughing in his live while his baby mama starts throwing shit at him and telling my husband he's not going anywhere. My husband is threatening to call the police since he has the custody agreement and she threw something else at my husband and said she's getting in contact with her lawyer. I was furious with my husband when he got back. Why would he do this? This could totally mess up his custody. Although since she's getting aggressive in the video they may decide neither should have my step son but why take something so serious and turn it into a joke? I asked my step son how he's feeling and he said "I hate my parents. They're fucking stupid." What did he get out of doing this?

@mommaof4 we don't have kids together. I don't want kids. I also told him it will look really bad and may backfire on him and he said "Well she's being violent towards me. They won't give her custody back." Well. My step son has been asking to live with his grandparents the last two years.... They may consider it now....

Edit: I'm gonna give a little back story about this custody battle and part of how his mom lost custody without putting too much of my step son's business out there. The short version is he ended up in my husband's parents custody when he was 9 for about 8 months and my husband was in jail at the time so he couldn't get custody. My step son is 15 now and his mom has been in contact with her ex boyfriend that was the reason she lost custody of him the first time because her boyfriend is a disgusting person and that's what my husband has been using against her in court but ultimately what made them give him custody was she missed court for the second time. There is so much that goes into this custody battle and a lot of back and forth and them both being absolutely horrible to each other and my poor step son is the one who had to suffer.