Not ignore, just discount, because such philosophies are actually offshoots of theistic philosophies. Without theism, such philosophies would not exist.
interesting statement. Prove it, or at least show your reasoning.
Moreover, disprove the following null-hypothesis:
In the course of his development, man developed a sense of supernatural or suspicious fear of the unknown. In order to comfort himself, to impose a satisfying pattern on a patternless world, Man invented various types of supernatural explanations. These supernatural folklore eventually developed into theistic religios creeds. Eventually, several societies of Man developed belief systems which discarded these uber-superstitions, discovering alternate means to impose a satisfactory pattern on their lives which had no need for hallucination, magic, faeries, or gods. Whether or not the gods of their forefathers ever existed, these new philosophies became completely independent of the ancestral stories concerning them. The are stand-alone creeds of their own, fulfilling the moral and ethical and emotional parameters of theistic religion - sans gods.