Has anyone ever had to deal with a troubled step kid. If so how did you deal with it and how did you build a relationship with them?

I’ve been with my boyfriend for 1 year and a half. He has a 4 year old son from another woman and his son is really difficult to be able to interact with. Ima be honest and I really don’t like his kid but I really want to like him and be able to do things with him. When I first moved in (January) his son would take my stuff and hide it on purpose, he had tantrums over everything. He hits his dad, grandparents and anyone who tells him what to do. He also peed on my stuff on purpose and has tried to break his dads finger on multiple occasions when he doesn’t give him all of his attention. He has also hit his grandmother in the face and gave her a bloody nose. He has been kicked out of daycare for hitting kids out of nowhere. His dad has said he’s always had these behaviors since he could walk.

My boyfriend is upset at me for not interacting and having a relationship with his son but idk how to. His behavior is out of control and no one seems to be doing anything about it. His son doesn’t like me which is a normal feeling with any step parent which I’m okay with but I would like to have a relationship with him and have us be content with each other and all of us be a family but his son has no discipline. My boyfriend and I just had our first kid together a month ago and I’m afraid to leave her alone when she’s sleeping during the day because I’m afraid his son could try to hurt her. It’s been really stressful for me. I’ve told my boyfriend that his son needs to see a child therapist before I can try to interact with him but he disagrees on how I’m going about this. He says he disagrees about not trying to interact with a child because of any situation.

Am I wrong for saying his son need help?