My stepson is a bully and I can't discipline him

My stepson has bullied my daughter and his own sister for at least the last year and a half, but me giving a shit about it is just too much. I can't say anything because he's not my blood. Straight from my kids mouth "I still love x and x, even if x is mean to me, breaks my toys, and hurts me." Now I've witnessed my kid get shoved off a scooter from him, he's jumped off a bunk bed onto a tent containing the two girls, kicked his own sister in the shin because he couldn't reach my kid, keep my kids phone from her and lie to his father about it, break his own glasses and blame it on my kid when she wasn't near him when it happened, he rolled over his own sisters legs with a bike because "she was in his way", mind you it was in the grass and he veered 10 feet off the driveway just to run over her, punch his sister the next day for no reason, reached over and smashed my child's face into a counter for no reason in front of his sister while my kid was just trying to get a spoon, and locks my kid out of a room every week they're here when he's not breaking my kids toys in her room. These are just a few of the issues we've had, I haven't come close to listing them all. Yet my concerns mean nothing and I'm the asshole for caring about all the kids and how they interact. My husband seems to think just making sure they don't see my kid should "fix" the problem and his son is "different" according to him. What happens when he's around just his sister? He bullies and hurts her. But my concerns mean nothing, I'm the d*** for trying to advocate for both girls and "you just hate my kids" from my husband because he won't whoop some ass or enforce timeouts or watch his kids when they're here because he's scared they won't want to come over. He was too into his PS4 game when a few of the occurrences happened. Pretty sure their mom don't know half of what has happened.