Metta-karuna (Pali: loving-kindness and compassion) are ethically, and perhaps morally, better than aggression, greed, and so on. Though someone may attack, curse, or hate me, I resolve not to do those things to them in return. Why? Because kindness and compassion are better than those things. A world full of kindness and compassion would probably be a nicer place for everyone to live than one full of anger and cold-heartedness, and cycles of revenge must be stopped somewhere. Also, there may exist something like karma or God’s judgment, such that unkindness, hatred, etc. may lead to a worse life for oneself in the future.
I am not saying that I am necessarily better than an unkind person, that my self/essence/soul is better than their self/essence/soul. (Actually, I suspect that we are all made of the same stuff, in different and changing configurations, whatever that stuff is.) I am saying that kind behavior is better than unkind behavior.
Of course, there are times when one must stand one’s ground. There is an art to standing firm but remaining kind. For example, if someone tries to steal my life savings, I cannot let them, but I can be as kind as possible in stopping them, and I do not have to chase after them looking for revenge. As I understand, liberal-majority states’ laws around the world about defending one’s body and property usually go along those lines, that avoidance if possible, or minimal sufficient defensive force if necessary, are best.
I am also not saying that I love it when people (or animals, plants, bacteria, etc.) mistreat me. I do not love that some people yell at me, threaten me, manipulate me, try to force their beliefs or preferences on me, are racist or nationalistic to me, try to cheat me, and so on. But I try to empathize with what reasons or life experiences might have prompted them to behave that way, I resolve not to hate them even if I do not understand them, and I try to treat them kindly.