Your point could be made even stronger by including people for whom it's even harder to feel compassion, i.e., someone who is deliberately cruel, rather than just someone who is dumb and isn't trying to fix that. However, even then, I don't think your "disgust" is entirely fair.
If we accept certain uncontroversial assumptions from cognitive science and biology, do we not come to conclusions, that for every person on Earth, if you were born with their genes, into their environment, you would be them?
I'm not trying to start a free-will debate, but this seems to me trivially true.
That's where kindness can come from. You don't have to excuse anyone's actions/stupidity/failures in their responsibilities, but instead of feeling "disgust", you could think of ways to help them from where they stand, or just let them be.
The most probable intuition behind the disagreements, it appears to me, is that "a person going around doing a bunch of good things and a little bit of bad-evil things is net-positive and we should keep him around even if we can't fix him, and a different person doing the same amount of evil things but not 'offsetting' them with anything is a bigger problem."