If A calls B a socialist or communist, however, then the burden of proof is on A to prove the charge, and the standard for guilt is so high that this is usually impossible. In this case it is A's reputation that is usually besmirched.
We live in an era of racial McCarthyism. It's all the more strange as the most powerful man in the world is black, and Arrington most likely voted for him. Strange kind of racist that does that. Strange kind of "institutional racism" that keeps blacks down in Silicon Valley yet gets the majority of the country (and the Valley) to vote for Obama as president.