It would be churlish of anyone to say that Catholics are not Christians, in exactly the same way that it is churlish to describe anyone who belongs to a Christian denomination as not being a Christian on specious theological grounds. That some Christians conlcude that they and they alone have the "Truth" is one of the burdens that those not of their number have to bear with as much equanimity as they can muster.
Being a Christian is a journey, not a destination. God and God alone will judge who is and who is not a Christian. Jack Chick will be out of work.
M:)RGANITE