Me Myself
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Says who? When one speaks of an Abrahamic faith they are referring to a faith which recognizes the Abrahamic god and the belief system attached to it. Even Devil worshipers recognize the Abrahamic god, they just choose not to honor or worship him, but instead find the opposite side of that coin more worthy of worship. The belief system is the same, the choice of who deserves worship and and how to go about worshiping are what differs. That's all.
One must say this makes great sense. While Abraham wouldn´t worshp the devil he had faith in the devil´s existence, just as he believed he was worshpped (at least by other angels) so yeah, Devil worship would be another tenet of abrahamic faith.