The only concrete example you’ve given here is your son telling someone the truth about how he feels. Children have no filter and I think you need to be really careful when teaching them about honesty. I wonder did you talk about why he didn’t like the baby? He really can’t help what he feels and the last thing you want to do is shame him for that. It’s all about learning what is and isn’t appropriate to say out loud.

I’m a big believer in positive reinforcement. He can’t be an asshole all the time. Do you take notice when he does the right thing and acknowledge his good behaviour? He has good parents and won’t be an asshole all his life, but sounds like he could do with a little less spoiling.