Why does he exist?

There is a boy in my group of friends that I hate a lot, we have hated each other since we were 6 years old. It turns out that I was going to have a birthday party and I didn't call him because we hated each other and he had the party on the same day, I had to give in because my mother said there was no way he could know the date, I went to talk to him at school and his mother went to complain to my mother that I had been rude, my friend said it was American school drama and I'm being a little exaggerated but I don't want someone who makes fun of n@z1sm at my party