I used to believe that things were either black or white. I was young, ignorant, and wrong.
Why am I talking about this? Today I realized that my pants are both too loose and too tight. It seems like it should be one or the other right? That is what you think if you are still thinking about duality.
For example, my pants are too tight because they press on my waist since they have an elastic waist. However, they are too loose because when I am walking they are so heavy that they start to fall. I bought them from a no-name online retailer and just like the other junk I bought, they have been more trouble than they are worth. Yes, they kept me warmer when I was commuting but I don’t need them anymore and I do WFH now. So they have been a burden. I am going to donate them after they are washed.

If you understand science then you know that even black and white aren’t opposites. We have a very simplified view of the world taught to us by mostly ignorant people. They didn’t keep up with the developments in science, so we believed things wrong and taught it to others as if we were right.
Kind people can be both kind and cruel at the same time. Cruel people can be kind in being cruel. I am not making a word salad here let’s give concrete examples from my life. In relationships to preserve the other person’s self-esteem, you may not tell them things that are wrong with them psychologically/spiritually. Ways in which their insensitivity and lack of empathy hurt you. So to be kind you break up with them or force them to break up with you. It seems you are being cruel, but you know that there is no future in the relationship even if they haven’t realized it yet.
Now a cruel person can be kind when they are cruel. People who were jerks to me helped me have compassion and kindness for people who have been hurt. It is a psychological fact that most people who hurt others have been hurt worse themselves. In that light, when others hurt you it is because they were hurt first or more, and that is sad. You can look at cruel people as sad creatures who haven’t learned to heal their pain. I don’t wish to experience cruelty but it has taught me a great deal about how people deal with pain. It taught me to have standards and to only be around people who value me. Even cruel people can do things that are kind without them realizing it.
Look beneath the surface. There is always more to learn when you interact with others.