That sort of view leads to "hate the sin, love the sinner" type arguments where I say that your homosexual behavior is horribly disgusting but I don't have anything against you as a person. (I'm not equating your point with that one, just giving an example where separating approval of a person's behavior from approval of a person leads to clear absurdity.)

I don't see the absurdity, actually. Seems on par for me with, "I think your taste in [death metal, anchovies on pizza, toilet paper roll direction] is horribly disgusting, but I don't have anything against you as a person".

Or for that matter, "I think what you say is disgusting, but I defend your right to say it."

Of course, AFAICT, this actually has nothing to do with what we're discussing, which is the opposite sort of issue: where one is, say, inappropriately disgusted by sports because when you grew up the people who were into sports were mean to you, so that now you make excuses not to go to the gym without really knowing why.

To bring this back to a more concrete discussion of Swimmer963's comment — if being "ambitious", whatever that means, leads people to behave like those high-school classmates of hers, then that should be a strike against being ambitious. Where is the fallacy?

Your statement only makes sense if there is a natural reality-clustering around the term "ambitious" -- or any other term. One of the techniques I teach people to use in this sort of situation is to ask if there are any ambitious people who don't display those annoying qualities, to focus attention on counterexamples. The essential idea is to cleave your brain's concept clustering to better match the diversity that exists in reality.

Sadly, our brains don't often update on this sort of thing without an extra push from the outside. A lot of common personal development problems essentially consist of this sort of accidental agglomeration of concepts.

Think of the story of the neural network supposedly trained to spot camouflaged tanks, which had in fact only learned to distinguish between pictures taken at different times of day. (Because the pictures with tanks were all taken during a different part of the afternoon than the non-tank pictures.) In the same way, if something always goes together during our formative years (like being ambitious and being an asshole), our brains learn that "asshole" is part of what the word "ambitious" actually means.

Correcting (and equally important, detecting) that sort of mistaken learning is what mindhacking (or at least the sort I practice and preach) is all about. Hence the heuristic of always questioning feelings of moral indignation or superiority: they have a strong prior probability of being a source of motivated reasoning and confabulation.

To put it another way, any time you find yourself indignantly arguing for the value of moral disapproval, the prior probability that you are engaging in confabulation motivated by your existing feeling of disapproval is pretty astronomical, regardless of whether your reasoning is actually correct.