Am I wrong?!

If you had a 3 year old nephew who regularly threw tantrums to the point he VIOLENTLY scratches his face until he bleeds or bangs his head on the ground over and over, hits his parents (heavily pregnant mama) Would you let your baby around him? My son is starting to pick up on some of his habits like yelling “MINE!!!!” And “NO!” (Which I know can be normal) but he learned from him to hit when he’s angry, luckily it was just once and I told him no and it hurts and he stopped but and I feel like its only a matter of time until he learns more bad behaviors.

My inlaws think we’re ridiculous and its a normal kid thing. My son is 19 months. He isn’t in in any kind of daycare so the way that he learns is by watching other kids and people that he’s around and looks up to other kids in his life.