A more relevant question - going back to Islam, might be 2Jn1:7 and how the "discern the spirits" question applies to Islam. From my standpoint Muhammed (and several other strands of Arabic Christianity that predate Muhammed) do in fact deny Christ coming in the flesh - so from that standpoint Islam is anti-kristos
, though the word in NT usage isn't as potent as in popular usage today. I mean Islam would be anti-kristos
in John's Greek terms, the anti-kristos
spirit then, but wouldn't be antichrist in popular English usage meaning a last days son of the devil.
2 Jn 1:7 For many deceivers have gone out into the world, those who do not confess the coming of Jesus Christ in the flesh. Such a one is the deceiver and the antichrist.