He was so afraid because he was so brainwashed that he actually forgot what emotions felt like. he wasn't afraid of Steve, he was afraid of the way Steve was making him feel. Dark shit man......
I just LOVE LOVE LOVE how every time the line "Every mother, every child, every brother-" came you made Bucky the child. Cause, yes. He is innocent, and pure, and being coerced into this, just like a child being given five dollars to bully a friend. It really shows that he isn't the one who did this.
the thing about Bucky is that he never got a choice in anything. You can tell from the first two letters of his serial number in the first avenger that he didn't enlist, he was drafted. He fought in the war because he had to, but the war won. And then he had his mind and his free will stolen from him and was brainwashed and tortured for seventy years.