He flinched, a visible recoil when Natasha brought up Peggy. His mind flashed immediately to their dinner just a few days before: the soft candlelight, the deep, ruby red of the wine, holding her hand as they exited the restaurant.
The fact that it had all been in public, utterly visible to anyone who might be paying attention. Steve had never learned how to mind his own expressions, had never succeeded in being anything but obvious when it came to how he felt, but it wasn't often that someone threw it back in his face like this. And bringing Peggy into it - that felt like a threat, even though he knew Natasha wasn't really his enemy. It didn't take much for his imagination to offer him a devastating scene, Peggy sprawled out in District 8's square, blood pooling steadily beneath her.
Steve couldn't look at Natasha a moment longer, couldn't quite keep from making a strangled, hurt noise at what her words had done to him. He'd been so sure, this time, that any further action on his part would result in his own death, that Stane wouldn't bother targeting someone he cared about this time, but that suddenly seemed far less certain.
He listened with half an ear to the rest of what she said, and there was that familiar jolt at being reminded once again that, technically, she'd done him a favor, however mean-spirited it had been. She was putting words in his mouth, too, because he hadn't called her a whore - hadn't meant to imply anything like that, and he was too upset and off balance to work through that tangled problem to figure out how she might have come to that conclusion. Steve just didn't know what to do with her, and it wasn't worth prolonging this conversation, not when he was as hurt and angry as he was, and not when she was lashing out with whatever would hurt him the most. (Because he wasn't foolish enough to think she'd scored those hits on accident.)
Steve flicked his gaze up to her, looking every bit as upset as he was feeling, and in the end all he said was, "You should put some ice on that eye." And then he turned and let himself out, slamming the door loudly behind him.