Why did Cain kill Abel? St. John says that it was because Abel was righteous and Cain was unrighteous and the unrighteous always want to kill the righteous. The unjust always hate the just. Those who delight in sin hate the saints. The unrighteous say, “Let us lie in wait for the righteous one, because he is obnoxious to us. To us he is the censure of our thoughts; merely to see him is a hardship for us, because his life is not like that of others, and different are his ways.”
Many people do not even live up to their own standards. They hate themselves for not being better, but they do not want to actually put in the effort required to be better, so they turn their hatred out on those who do. Consider the hatred directed at those who have many children by those who use birth control. Consider the hatred directed at newlyweds who were faithful to chastity by those who have never practiced it. Consider the hatred directed at those who serve the poor by those who serve themselves.
This hatred first takes the form of ridicule. They call the saints fools. They call them repressed and psychologically immature. But if ridicule does not work, if the people are obviously happy doing what is right, clearly happier than those who choose sin, the hatred becomes an accusation: The sinner thinks, “I cannot be good, therefore no one can be good. It is not possible. They are just pretending.” Finally, the hatred become pure anger. “How dare they live according to some set of rules? Do they think that they are better than the rest of us?”
It is this hatred that is behind martyrdom. It is because of this hatred that 80% of religious persecution in the world happens to the 20% who are Christian. This is the hatred that killed Abel. This is the hatred that killed Jesus Christ. This is the hatred of Satan himself who cannot stand that anyone should go to heaven when he does not.
We have to admit that this hatred is a danger for every one of us. We are all susceptible to the temptation to hate those who are better than us. Do not be deceived just because you do not kill the person you are jealous of; everyone who hates their brother or sister is a murderer.