Why Do American's Hate Communism So Much?

If you can't figure it out then my telling you will do no good. You obviously are not very well informed about what it is like to live under communist rule. Let me ask you this. If communism is so great then why can't the citizens come and go in and out of their country at will? Instead they are basically imprisoned within their borders. Remember the Berlin wall? Why are people willing to risk their lives to get to the US?