It's a false "love".
It's probably not even a false love. Like you said, love is subjective---and like I said, love does not come with a moral code.
There was a time when it was fine to beat your wife---nobody would question if the husband loved the wife, because it was culturally acceptable. It would not have even dawned on them to declare 'if you love your wife, you would not beat her'. Because, culturally, that was how it went. You could beat people you loved.
A slave owner can love their slaves, and rationalize their behavior any way they like.
Most abusive parents actually love their children---but they have no self-control, or a poor understanding of what works. We look at it, and we say they don't love them, but if you ask them, they do indeed have a loving feeling in their hearts----it's the other stuff that is screwed up.
Love is not a LAW. LOVE is an emotion. How people treat those they love is cultural. Jesus came from a slave holding culture. So maybe he was just telling people to love their slaves---I think most of them would have thought that at the time. Sometimes, love is simply not enough---we aren't living in a Beatles song.