Everything about this place has Tony on edge. He's paranoid and hesitant to trust because he's not who he was back home. Well, he's still Tony Stark, but he's Tony Stark stripped of everything he had and what he considered to be a part of who he was. This isn't like it was back home, he has to be careful. Watch his step. Not go out and broadcast to the world who he is and what he can do even if he really really wanted to.

So he's going to be suspicious of this guy and his fancy schmancy scrap metal gun and his LED spine, even if it looks like he could know his stuff. Leer a little. Size him up. No big deal.