They have been one of the top three contenders for pretty much all of the last twenty seasons, and did so in a generally classy manner and with good football. No doubt the fans of their rivals resent them for that, but surely they also respect them, however grudgingly. The way I see it (though I'm not sure how common that view is, and in any case it's an outsider view of both British and American sports), they're a bit like the San Antonio Spurs - you don't have to like them, but they're remarkably consistent in the quality of their play and are difficult to hate or despise (and I say that as a Liverpool and Suns fan!). Though that might also make them a somewhat unexciting choice of team to root for.

If you want a team hated by its non-fans, you'll have more luck with Chelsea or Manchester City, both of which have developed a reputation for trying to buy their way to success (like the Miami Heat, while we're at it).