Existence of Marcion questioned?

[JairCrawford]

Here is what Justin Martyr wrote of Marcion of Pontus:

And there is Marcion, a man of Pontus, who is even at this day alive, and teaching his disciples to believe in some other god greater than the Creator. And he, by the aid of the devils, has caused many of every nation to speak blasphemies, and to deny that God is the maker of this universe, and to assert that some other being, greater than He, has done greater works. All who take their opinions from these men, are, as we before said, called Christians; just as also those who do not agree with the philosophers in their doctrines, have yet in common with them the name of philosophers given to them. And whether they perpetrate those fabulous and shameful deeds--the upsetting of the lamp, and promiscuous intercourse, and eating human flesh--we know not; but we do know that they are neither persecuted nor put to death by you, at least on account of their opinions. But I have a treatise against all the heresies that have existed already composed, which, if you wish to read it, I will give you.

Then later, 

CHAPTER LVIII -- AND RAISE UP HERETICS.

And, as we said before, the devils put forward Marcion of Pontus, who is even now teaching men to deny that God is the maker of all things in heaven and on earth, and that the Christ predicted by the prophets is His Son, and preaches another god besides the Creator of all, and likewise another son. And this man many have believed, as if he alone knew the truth, and laugh at us, though they have no proof of what they say, but are carried away irrationally as lambs by a wolf, and become the prey of atheistical doctrines, and of devils. For they who are called devils attempt nothing else than to seduce men from God who made them, and from Christ His first-begotten; and those who are unable to raise themselves above the earth they have riveted, and do now rivet, to things earthly, and to the works of their own hands; but those who devote themselves to the contemplation of things divine, they secretly beat back; and if they have not a wise sober-mindedness, and a pure and passionless life, they drive them into godlessness.

Of course, if you've read Justin, you know he's pretty dumb.  Declaring a single deity in one phrase while affirming demonic magic in the next.  Marcion rejected the god of the old testament, and claimed that vengeful bastard was not the supreme god who sent Jesus.  So that's why Justin and Irenaeus took exception.  They wanted the old testament god to still matter.

And said declaration of said single deity and confirmation of demonic magic continues to be taught in many mainline Christian denominations, ‘yea even unto this very day’.

And those were precisely the quotes I was thinking of! Thanks! To my untrained eyes, his mention of Marcion does not seem like an interpolation of a non existent figure by a later scribe. However, the polemic is very real indeed.