Yet can't you envision e.g. transhumanism being tabooed like that if found to be "ineradicably tainted" by the human lust for power and an insidiously corrupting desire for a "legitimate" reason to feel superior to the people you currently associate yourself with?

That's a common argument against it, actually, although it's usually framed in class terms. Maybe the most common once you filter out all the various manifestations of "ew, that's gross".

Not one that I accept myself, but like I said I only buy an approximation of the thinking above. There's plenty of places it'll steer you wrong at the margins.