I do not call what I do not like "evil". That does not mean I respect/accept/forgive what I do not like.
In that case, we're arguing about semantics. I agree that good and evil are, to a great extent, relative. But that doesn't mean they're meaningless.
We can reach a functional understanding of what we mean by the concepts the same way we can reach a functional understanding of what we mean by concepts like "bird" or "fish." That is, by pointing at things, classifying them as one, the other, or neither, and then trying to identify commonalities between the things we grouped together. So if we've got things with beaks, wings, and feathers in one basket, and things with gills, fins, and slimy skin in the other, we can provisionally declare that a bird is a living creature with a beak, wings, and feathers, whereas a fish is a living creature with gills, fins, and slimy skin. We can then refine and adjust our definitions as we learn more about birds and fish... or good and evil.
Eventually we'll hit something that we don't agree about. That we can also deal with, simply by classifying it under "things we don't agree about."
So: Hitler, evil. Gandhi, good. Kicking a kitten, evil. Adopting a stray kitten, good. Rape, evil. Consensual sex, good. Taking something that isn't yours, evil. Giving something you have to someone who needs it, good. And so on and so forth. Get my drift?
I also have a Nietzsche-style suspicion against them who declare themselves "the good guys".
As do I.
I just see people acting according to their nature, the way they brought up to be. If you want to change that you simply have to try to understand their perspective.
A very commendable approach.