Nothing wrong with him at all. he's just a bloke who is in a group and writes songs that some people like and some don't.
I think the hate has been built up over the years mainly by the press because he likes to keep his private life private and doesn't play by their rules (i.e. interviews and smiley pics with the family).
There are a lot more singers and song writers out there who are much more annoying than Mr Martin and one of them has a surname that sounds like twunt