You want me to believe something not realistic? Fine. Give me a reason first. Thor is a demi god from another world. Hulk was exposed to radiation (I think? Never saw those). Captain America did his thing in the machine. Stark was a genius and made a suit of armor. What do we know about Hawkeye? Some criminal merc that happens to be better with a bow than a gun? He's portrayed as 100% human, and therefore anything behind human that he does causes concern.