Between the fire against his skin (and discomfort of it), the change in Zerxus' eyes and growl that Steve comes damn close to just straight up punching the guy in the face. That is a display designed to get a reaction and it is effective.

Steve's only got one response to adrenaline - maybe one and a half - and it's not flight.

Fortunately (mostly for himself, here) he's reckless, but doesn't have a hair trigger. A couple of deep breaths and his shoulders relax back again.

"You're more than welcome to protect me. Because at least with me, as far as it can go, your decisions are yours. What you don't get to do is tell me what I feel about what's going on or what comes out of your mouth, or what I say in response to it. Those are mine. Turning into a bonfire with a sore throat isn't going to make me decide you 'deserve' the shit that's happening anymore than reminding me you chose will. Maybe try the wings next time. Those were fairly intimidating."

Pissed? Yeah. Also 'bonfire with a sore throat' like he hadn't had a moment of very real fear, there. Intense real fear, even.

Yet... he's still in physical contact, not fighting the grip, just leaving his hand in place over Zerxus' heart.