IF Christianity is a subset of Religion and IF Religion is
   defined ONLY by the subset: (the set being: "a pursuit or
   interest to which someone ascribes supreme importance." and the
   subset being "the belief in and worship of a superhuman
   controlling power, especially a personal God or gods." ) AND IF:
   belief is a required property of religion and therefore its
   subset, Christianity AND IF Atheism is defined as "disbelief or
   lack of belief in the existence of God or gods" AND IF belief in
   the existence of God or gods is a requirement of at LEAST
   Christianity (subset) and possbly the whole set (Religion) THEN
   (perhaps) there could be something to debate about. That is, if
   those were definitions I considered to have exclusive validity.