I believe there are two things going on with Hamilton at the moment.
As discussed before, arrogance is welcome, but it needs to be correctly channeled. I've had my doubts about him since the "monkeys at the back comment" last year, which is spectacularly arrogant, disrespectful, and can you imagine the fuss if a white driver made the same comment, even though there was no racial edge to it at all? Recent personal experience allowed me to be fortunate to witness some outstanding driving and then later hear a complete arse, which did nothing to diminish my thoughts.
Secondly, there is a peculiarly odd "Brand Hamilton" thing going on that leaves a strange taste in the mouth. This is not entirely his fault. I think he is poorly managed, actually (*), and being told by dad you can't do one thing that you agreed to, however tongue in cheek it was, and then to turn out a week later "racing" a Learjet as a "Learjet Brand Ambassador", no less, leaves me feeling very cold towards him.
He is a cracking driver. None of my opinions towards him are formed by the UK tabloid press, or just because he makes mistakes. I've made plenty in my career and have been forgiven by my paymasters and by my critics. He should be no different. However, if he doesn't win the championship this season then I don't believe he will with Mclaren. Unless they can get back someone like Raikkonen, I'm sure they will start going backwards relative to BMW and Ferrari, and possibly Renault, and then Hamilton will suffer as a driver.
Personally I don't back a driver just because they are British. I've always thought Button was terribly over rated (not something you can level at Hamilton actually) and Coulthard, as Jon Hardcastle said, continually under achieved.
(*) I agree with what Jackie Stewart has suggested about introducing personal trainers to F1. I believe that all of the drivers need someone that is soley interested in managing the athlete, rather than the money making machine.