“Funny. When it comes to fighting, you can see how a dodge like that is a problem,” you reply. You make a point of sounding confident, even smug.
“You trying to say something?” he grumbles.
“You don’t want to help because you think it’ll make things worse. Or maybe just that you’ll screw up somehow and feel bad. But you’re not thinking about how much it hurts your pride to be sitting out here in a decrepit shack when there’s a whole wide world out there. A whole wide world where you could be making a difference, and you’re choosing not to.” You stand up as straight as you can, focusing on your words to avoid thinking about the pain. “You dodge chances to help and you just hurt yourself more than if you’d taken the hit.”
“I remember when I was young and thought I was clever like that,” the grebling mutters. “You don’t understand me at all. Get out of here before you hurt yourself any more.”
A lot of people would take a line like that at face value. But you notice that he wasn’t actively telling you to go away before, even if he clearly wanted to.
So what your instincts tell you is that you’ve struck a blow. And now he’s worried about what will happen if you stick around. Which means you need to really press your advantage now and say or do something he can’t dismiss so easily.
“You’re not angry at me. You’re angry that I might be right.”
“Tell me the story that made you quit.” Show him you’re genuinely interested in helping him, not just getting the artifacts
“Who did you lose?” Showing you have a complete read on what he feels
Stop arguing completely, sit down, plant your sword and lean on it, letting him know you’re not going away. Calmly let him know you’re not trying to convince him or changing his mind, you’re just here for a little help with saving innocent lives, surely he once felt and acted like you are right now