Freethinker: somebody who does not accept dogma: an independent thinker who refuses to accept established views or teachings, especially on religion.
Freethought is incompatible with theism. The very nature of freethought is an anathema to religious belief. The rigid doctrines of many religions creates a mental state wherein everything is looked at and evaluated from the viewpoints of that dogma.
Theists are asked to believe solely on faith, blind unthinking faith is required to accept many of the propositions presented by various religions. As a result many theists become vulnerable to manipulation and can be convinced of propositions which have no basis and cannot be proven. Hysterical alarm about this or that harmless situation, law, or occurrence is very possible. I have seen religious co-workers create hysterical imaginings about any little change made at work. Anything that might produce change is feared and avoided.
Freethought, and to be a freethinker is a requirement for the intelligent Atheist. The prevalence of religious belief within the United States is such that freethought, outside the box of dogma, is the only way an individual can escape from and stay free of religious influence.
The religious believer, inside the box built by his/her religion, fears atheists. They fear the change that atheists represent, and see atheists as a threat to their way of life, their children, their beliefs.
Unless religion is forced to accept change, religion must be eradicated, to guarantee the survival of the human race. Christianity in particular puts forth a doctrine of doom, toward which, consciously or subconsciously the believer works to make come to fruition. Numerous wars have been fought, will be fought, unless these doomsayers are either kept out of public office or eradicated by forcing change.