I discover, sometimes, that things about others which I detest are qualities of my own which I detest, reject, and attempt to disown by pinning them on others.
Although I am not a Borderline Personality, there is an element of projective identification in this. Whether in fantasy or in reality, we can mentally construct another person so as to contain, embody (or, if the person is in our personal lives, to even get them to enact) our own rejected demons. Then we can detest them or look down on them while preserving an illusionary and undeserved self-esteem.
I have learned to reflect on the qualities I seem to be most irritated by or contemptuous of in others and to do a little reality check to see whether it's more about my stuff than about theirs.
Do you find yourself doing this sometimes, as I do?