I think your definition of "strong atheism" here is a strawman.

You as a Catholic do not belong to a religion that consists of "rejecting the Quran." In fact i would imagine that you would strenously object if someone told you that you belong to "Religion X" which has as its belief "rejection of the Quran." The Quran is someone else's assertion, and you as a rejector of it do not thereby subscribe to a belief.