Pigs are very dangerous animals. I was nervous about raising them because I had a small child. I thought him to be afraid of the pigs just to be safe. Your grandfather knew what he was talking about.
I can't figure out exactly why they didn't like him. He was castrated, and not related to any of the others. Those are the only factors I can can think of that might have contributed. He was never aggressive toward the other pigs, which might have worked against him. I always felt sorry for him and hated to see him go they way he did.