If you are debating a Protestant, someone who belongs to one of the denominations founded by the 16th century reformers and their successors, who knows and understands his faith, you have no need to prove the fallacy of the Rapture because they do not believe in it. If you are debating someone brought up in a Protestant tradition who has forsaken his faith to buy into the Rapture fallacy introduced early in the last century as an innovation that denies the saving action of Christ on the Cross and the efficacy of the Resurrection, then you are not even debating a Fundamentalist, who bases his belief solely on scripture, in which the Rapture has no basis. You are debating a non-Christian cultist, similar to a Mormon or JW, who denies Christ so that is where you have to begin your argument. A study of the early fathers who challenged Arianism, especially Athanasius, is the place to start.