for a few reasons:
1. weaboos make people think all anime is weird and the people that like anime are weird.
2. it's like a bunch of adults watching a little kids show. like a person being into super hero comics and that's seen as geeky.
3. if it's related to art, then people say anime is boring and it's not original or creative like cartoons. (so they hate anime artists)
4. too serious and not goofy enough for people who prefer cartoons.
those are some reasons people don't like it. people are just people, some are just really mean. have to just ignore it and just enjoy what you like doing.
