I cannot bear to consider a real example of this, so give you a fictional one.
In The Fall, a senior police officer visits a paedophile priest in prison, hoping for background on a suspect. The paedophile refuses it, though he would answer the questions if the Catholic police officer addressed him as “Father”. The Church had defrocked the paedophile, but he refuses to accept that this is effective; he claims to remain a priest. He says that the boys in his care desired what he did to them, and that they benefited from it, and that it was a proper discharge of his priestly functions in the care of the boys. He is resentful that his service to the community is not properly recognised, and at his imprisonment, thinking it wrongful. He speaks throughout with certainty.
What would that be like? Can we feel with such a person?
I imagine his feelings would be overwhelming anger and resentment, with a sense of his own integrity and rightness, that is, the self-acceptance which is such a boon for the rest of us. I wonder what it would be like to believe that the child-victim wanted, or deserved, the sexual attention, or alternatively that the child-victim had no value, so could be used for the man’s gratification. A man like that could destroy so many lives beyond hope of repair: his direct victims, and all their loved ones. Yet compassion is the only response, to understand the man, or to respond to him.
After all, the world is full of people with equally deluded beliefs, harmful to others- young earth creationists, holocaust deniers, climate change deniers. There are psychopaths who see no value in others. There are those who see war as the only way to defend what they value, and arms dealers, wicked souls who make profits from making and selling tools to kill people and destroy things, which are sometimes used to threaten and coerce.
The paedophile who cannot accept that following his urges is wrong, or who cannot control his urges, must be locked up until he is no longer a threat to the rest of us. The arms-dealer hob-nobs with the rest of the super-rich, and dies old and happy.
Compassion is not just a way of getting warm feelings when we contemplate those less fortunate than ourselves, but a tool for understanding the World.