Why do people hate?

Yesterday was grandparents day at the girls' school. The kids were supposed to invite their grandparents to come to the school to see their classrooms, meet their teachers, and just spend some time together at school. It's a really cute idea; they used to have it at Secrest too and the kids always enjoy it. Well, the girls invited my parents, which was probably a mistake, seeing as how my dad is becoming more and more antisocial. They went to Karry's class first, where my dad grumbled incessantly about the room being cluttered. I have noticed when I've been there that the room could use a little organization, but with that poor teacher having such a wild and unruly bunch of kids this year I can imagine it probably takes all she has just to cover the curriculum, much less spend her time cleaning up the classroom. The worst part was when they went to TJ's class though. Since February is black history month, TJ's class has been spending a lot of time learning about famous black people who did important things. The teacher has been trying to find out unusual facts about the different people, besides just what they contributed to history, to make it a little more interesting for the kids, and TJ has been really excited about what they've been learning. My dad definitely put a damper on that though by storming out of her classroom yesterday, complaining about them having to learn black history (TJ didn't exactly tell me what he said, but knowing my dad's Nazi-like beliefs and penchant for profanity, I can imagine). Poor TJ was totally embarrassed and I am just furious. Dealing with my dad's racism has always been hard for me (and my mom and sisters). Being forbidden to invite black friends to the house or talk to them on the phone, being forbidden to date guys who were black or mixed, as well as Hispanic, Italian, Greek, Middle-Eastern, or had a last name that ended in a vowel, was difficult and sometimes embarrassing, and I guess it's really a blessing that my sisters and I didn't grow up sharing his beliefs. It's probably because we went to a city school where we encountered people of all different backgrounds, that and the fact that my mom made it clear to us that she didn't share his beliefs either. Still, I just don't understand why he feels that way, or why other people do. It's frustrating, and it's sad.