He feels sick. Steve isn't arrogant enough to think Tony did that to prove him wrong. Apparently he was a factor. Good old Captain America making an impression on the youth. God how could he be so stupid? Tony may be older than him physically, but he grew up with the fairy tale. Of course his words would effect him. The color drains from his face and he can't look at Tony anymore.
"I already told you what happened. SHIELD is HYDRA. They sent a brainwashed man after me and my allies. We fought, we won, and now I have to make things right with him." Everything except for the identity of man he wronged so deeply. Isn't it nice the way he keeps ignoring that one?