I wasn't aiming at that particularly, I was attempting to point out that there is a difference between flirtation and harassment, but that no-one knows where it is: this position is made infinitely more of an issue when there is a power disparity between the parties.
... using any "power" that is obtained is a natural consequence: the ability to use power is one of the prime reasons (maybe at bottom the only reason) for seeking to obtain it. Having that power used on you is unpleasant, and is currently defined as "abuse".
There is no question that there are muddy areas between flirtation and harassment. The problem comes in when one must draw hard clear lines, as would be required of any kind of juridical situation. The latter may strike you as arbitrary, but I'd argue that it's well nigh impossible to do otherwise. The subjectivity involved in such draftsmanship is thicker than a custard.
As for the second point? It seems a bit of an overgeneralization, one that throws the baby out with the bathwater. There are enlightened and then despotic exercises of power. Not all fit the characteristic of abuse, simply because such power is wielded upon subordinates. The problem comes when the exercise is solely to satisfy the will of the wielder to the clear detriment of the subordinate. There's plenty of unambiguous examples of such abuse that have little to nothing to do with sex.