Being open minded does not equate with agreeing with your views. You are free to express your beliefs as we are free to express ours disagreeing with yours.
Personally, if someone wants to believe that socialism/communism is a, "good," system, I don't care, they can think whatever they want, but the second they take that belief and put it into active attempts to institute it in this country, they then become an enemy of the constitution because communism and our constitution cannot co-exist.