I fucking hate my brother in law

I just spent the entire week with him at the beach for Christmas and I’ve always sort of hated him, but it’s at a new level now. He is such an egotistical type of person. We spent time with his future brother in law and sister in law and he decided that as soon as he left that he would bash their parenting skills and just straight up talk shit about them. He doesn’t even have a kid! Like why do people feel the need to talk shit about other people. It just makes me think that as soon as I leave he talks shit about me. I swear if I hear him talking shit about someone one more time I’m going to smack him. Anyone else have any stories of issues with their brother in law?