Because you cannot be loved by everyone! And seriously we don't give a fuck about those who don't like her! It's their problem if they can't realize how beautiful she is in and out! And she is talented! :)
It is because they know nothing about her..I was the same(dont hate me for that) before I started to actually look into what she is about and I have actually made other people see her for real too I point out that she is a real musician she is a piano virtuoso and that usually makes people think because she isnt just another generic pop star that cant write music or play and has been manufactured to make money ie bieber.Also the fact she is hands on with her charity work going to brazilian schools etc.Alot of people think she is ugly because all they have seen of her is un flattering pics in a womans weekly magazine so to put it simply it is just ignorance;Tell these people to go educate themselves and then come back to you about it
I think there are many reasons. At first - the don't know anything about her, they've only seen few videos, scandalous clothes or believe rumors. Second - they have no life so that's why they judge her. Third - they don't stand for equality. They think they're better than her and others.