Yes this is a really interesting subject. I think you are right, there's got to be a consideration of the intent behind a destructive action. If you harm someone, it has to matter whether it's in self-defence or not. If you are in a position of power, you don't just attack someone in a weaker position. Remember how Bilbo spared Gollum. There are many more examples.
During the session, I threw a number of messages at Corey, and he picked up a couple of the more intelligible ones. I was trying to make the case that it all has to do with the Music. It's more or less what MithLuin is saying. When an elf uses magic, which they seem to do almost all of the time if you are looking with Sam Gamgee's eyes, they are working with the Music and their own understanding of it. They are experts at bringing out the hidden potential in everything that is Arda. Their creations are acts of love - and their creations love them back, making ropes untie themselves when necessary, boats avoid capsizing etc. When Fingolfin reforges his sword, he uses his understanding of the Music. All of his experience of the crossing of Helcaraxë, his people's suffering, their struggle, their losses, the loved ones who were lost - Fingolfin processes that in his soul and the pain and sorrow, mixed with the more positive feelings of satisfaction when making it, etc., becomes wisdom, that is, understanding of the Music. He uses that deep insight into the plan of Iluvatar to make his sword powerful.
That is different from how Sauron would do it, of course. His mission is to enforce his will on the world. That is the extreme opposite position. The intention is to change the Music.
Ok so perhaps that was a digression... Well, consider that Eru has put everything in the world for reasons, and that everything has an intrinsic value - but add also that the most important in his creation are the Children. They have certain needs that they cannot satisfy without affecting the world, so that has to be part of the Music. But, as you say, when the intent is to just destroy, that is wrong - it is an act of opposition to the Music. And dominating someone is to be in a position of power and using it to restrict their possibilities of fulfilling their potential - fulfil their part of the Music.