Weakness

The cruel always believe the kind are weak.
David Frum "The Real Lesson of My Debate With Steve Bannon"

But, I would submit, even the worst torturers never believe themselves to be deliberately cruel in the sense that they derive pleasure of satisfaction from the simple ability to cause suffering. People tend to equate Cruelty with Evil, and no-one (outside of perhaps the insane) understands  themselves to be Evil. I think that the cruel believe that they have mastered that part of themselves that argues against Doing What Must Be Done, and they see the kind as weak, because they see kindness not as the best means to a desired end, but as giving in to personal qualms against hard choices, difficult things or the toughening power of suffering.

The very fact that weakness is considered a personal flaw is perhaps the real problem that needs a solution.Once a certain kind of strength becomes a necessity to be considered a worthwhile person, and people compete to display it, denigrating others becomes worthwhile. And in a world where there is no worse insult that to be lesser, making weakness lesser encourages people to find ways of seeing it in one another.