Don't leave something because of haters. Thats what they want to happen. Rainbow Dash is a wonderful character. She has a lot of reasons to be liked. She is pretty much tied with my favorite pony Pinkie.
Why do you care what other people think, to a point where you'd stop liking a character? All the characters have haters and all of them have lovers. Determine what you like based on what you enjoy, not on what others enjoy.