Why do people who like harry potter hate people who like twilight and vice versa?

i LOVE them both? buuuuuut i did find somethings in harry potter that twilight clearly copied off, such as penelope clearwater (percy weasleys girlfriends) and then in twilight its harry seth leah and sue( is it? lol) clearwater..and the fact that there is sirius BLACK and jacob BLACK but these aside i think they are both good books i hate this tension between the books :P I DONT UNDERSTAND IT lol :)