Moloch is at work here. Pretend that all open American racists advocate quarantining U.S. Ebola victims, and I'm not a racist but I do believe in quarantining. My opinion on quarantining will have almost no impact on U.S. policy, but will cause people to increase their estimate of my being a racist so it's in my self-interest to either oppose quarantining or to keep silent on the issue since I don't want to be perceived as racist. If all non-racist do this than supporting quarantining is strong evidence you are a racist.