It's actually the thing I like most about him. I love all the prompts that place him as dominant in aspects of the relationship, I really do, but for me there's nothing more heart warming than someone being gentle and valuing free will over everything else. For all his power, for all his knowledge, and even for all his faults where he messes up, those are the traits I find most appealing to his character.
Thiiiiis. Reminds me of the Mercy riddle in DAO,
"she wields the broken sword, and separates true kings from tyrants." The fact that he's gentle and knows when NOT to fight is one of the most attractive things about him, as a friend, lover, and ally.
Iron Bull: Nice job in that last fight, Solas. You really kicked the crap out of that guy.
Solas: I suppose.
Iron Bull: [scoffs] What, you don't think so? You ripped him a new one! It was great!
Solas: Unless the fight is personal, violence is a means to an end. It isn't appropriate to celebrate.
Iron Bull: [sighs] I don't know. Gotta wonder about anyone who fights as much as we do and doesn't have some fun with it.
Solas: We have fought living men, with loves and families. And all that they might have been is gone.
Iron Bull: Yeah, but they were assholes.