Some people just need something at which to direct all the negative energy they carry around, if they don't find a way to offload that burden then it'll end up being turned back in on themselves, and that can be too much for some. Better to jump on a hate bandwagon and seethe the day away
I think the problem is that Kleins are seen (rightly or wrongly) as status symbols, as are BMW, Audi, and Mercedes' cars, and status symbols are profoundly vain and self-centred things: their point is to indicate to anyone and everyone else that the owners of the symbols are somehow
above the norm, the hoi polloi, the mass of humankind, and especially above the poor. If status symbols are used to indicate some sort of vague, abstract superiority over others, then it should come as no surprise if others don't like that very much. Additionally, people who are essentially selfish and arrogant in one aspect of life are likely to be selfish and arrogant in others. Even more cause for them to be disliked.
However, as is evident in this thread, there are also Klein owners who do not appear to be at all interested in their bikes as status symbols; indeed, the fact that Kleins are seen as status symbols is a drawback for some owners, an embarrassment even. They like aspects of the ride, the engineering, the paint, whatever . . . And that's all. Your earlier post, describing how much you enjoyed riding yours, was a glowing example of this attitude. In fact, it's the only thing I've ever read about Kleins that made me think I might like one.
But, Kleins still have a double aspect: snob value for the vain, engineering value for genuine enthusiasts. As long as that persists, they are likely to be divisive.