It would actually be better for evil people to learn how not to suffer from bad situations so they can control themselves and keep their minds on an even keel. That would be much better for the world.

"Goodwill [mettā] and compassion, all the brahmavihāras, are another set of the guardian meditations. Think about how you’d like a happiness that doesn’t harm anybody, partly because you feel empathy with other beings and partly because you realize that if your happiness depended on other people’s suffering, it wouldn’t last. They would do what they could to destroy it. So you want a happiness that doesn’t impose on people. And because this is a happiness that depends on your own inner resources, you find that your true happiness doesn’t conflict with anyone else’s true happiness. So you wish them goodwill. May they be happy too. May they understand the causes for true happiness.

Now, as you do this, you may find that part of your mind says, “Well, there are certain people I would rather see suffer first for one reason or another.” So again, think of it as a committee meeting. You’re sitting down and you say, “Okay, exactly why? What would you gain from that person’s suffering?” As we all know, most people do evil because they’re feeling threatened, they’re feeling miserable. They say, “As long as I’m miserable, let everybody else be miserable, too.” That’s what they think. So what would be gained by that person’s suffering?

You say it doesn’t seem right. They’ve done so much evil in the past that it doesn’t seem right to let them off the hook. But you know the principle of kamma is such that the results of your past actions do not totally determine what’s going to happen in the future. It would actually be better for those people to learn in the meantime how not to suffer from bad situations, so that even if bad situations do come up, they can control themselves, they can keep the mind on an even keel. That would be much better for the world.

That story of Angulimala, the murderer who later became an arahant: When you find yourself identifying with Angulimala, it’s a really nice story. When you find yourself identifying with the victims or the families of the victims, it’s a pretty upsetting story. So, which side do you want to be on? You recognize, okay you’ve probably done a lot of unskillful things in the past. If you want to believe that you can train your mind so that you don’t have to suffer from the results of your past mistakes, you should give the same right to other people. As we’ve seen over and over, vengeance doesn’t really solve anything. When people suffer a lot, it doesn’t necessarily make them wise and compassionate.

So, try to sort through whatever resistance you have to the idea: May all beings be happy. When you sort through it, you find it easier and easier to stick with the practice. The next time that you call up those thoughts of goodwill, they really do feel nourishing. You find yourself more and more aligned with them. And when you can have goodwill for all beings, it becomes really hard for you to do anything unskillful because you don’t want to harm anybody."

~ Thanissaro Bhikkhu "Training the Committee"