Terpstra isn't much of a *** or arrogant, it's more that he is a bit of a petty person. He always reminds me of the kid that has always been pampered and can't take any form of criticism and/or sees criticism everywhere. I don't really get his attitude - he has always been really childish towards Rabobank and their (Dutch) riders too - because he achieved more than most others and got there by choosing his own path entirely, which is admirable. But still he whines a lot (I must admit, his accent makes everything look a bit whinier than it might be and that's obviously not his fault) and points his finger at futile things, when a rider of his talent doesn't need all that. But maybe he uses all these things as some sort of fuel to improve himself, I don't know.
Sometimes - like in the quote in Dekker_Tifosi his post - he is really funny and when he is relaxed he is a pretty nice guy actually. And even though sometimes he talks huge bs, he is not afraid to speak his mind. But someone like Lars Boom isn't afraid to do so as well, but always seems focused more on himself than on others (when Boom crashes it's part of the race and most likely his own fault and when Terpstra crashes it's someone else's mistake - preferrably someone 17 minutes behind). Plus he was always trolling Niels Albert, which obviously makes him a hero.