Edgar, how is a simple lack of belief in something comparable to the African-American experience? We are still saying that "atheism" is a simple lack of belief in God, right? Do you really think it is appropriate to compare atheism to an ethnicity?
And What exactly do you mean by "speak out"? Confronting other peoples beliefs causes conflict. Confrontational Christian leaders are met with as much opposition and disdain as confrontational Atheists like Richard Dawkins. Dawkins et al. are going after people's beliefs and attacking any public display of religion. This is their right, but people fighting back is at least understandable.
When you get into peoples face about their beliefs you can expect to fight back whether you are an atheist or not.
As an atheist, I don't think the persecution complex is warranted. It is not fair for anyone to throw punches and then complain when they get hit back.
Those of us atheists who are tolerant of other people's beliefs don't seem to have a problem.