Really no one here, who knows it can by joy to hurt someone?
The joy of demonstrating ones power, ones might.
Or joy dominating someone and being able to ...
So if you don't know feelings like this, why do you practice a martial art?
Why do you practic techniques which will hurt, maybe badly your opponent? (hiji kime osae, irimi nage, atemi nage ...)
Do you really feel no joy when controlling uke?
My joy, whether as nage or uke, is in the challenge of finding and maintaining connection. We join together, it is both our energy making it happen. Frankly my greatest joy, what makes me laugh out loud, is when as uke I find myself on the ground w/ no idea how it happened.
I also want to point out that domination and the power dynamic of domination and submission does not necessarily have anything to do with hurting the other.