mlinssen,
What I am saying is that Mark is not copying the Marcionite gospel. He does share a source. But he did not introduce the Baptist character. This character was already extant in the source that both Mark and the Marcionite author drew from.
The evidence is throughout the Marcionite gospel itself, as it references back to the baptism scene missing from that gospel. We see John referred to as the Baptist in the Question of Authority (Luke 20:1-8), a story attested in Marcion. Although we cannot say exactly what the full wording of the story was in Marcionite form, we do have paraphrased snippets preserved by Tertullian (AM 4.38.1-2) confirming the passage and the reference to John's Baptism.
Christ knew "the baptism of John, (baptisma Ioannis) whence it was." (Luke 20:4) Then why did He ask them, as if He knew not? He knew that the Pharisees would not give Him an answer; then why did He ask in vain? Was it that He might judge them out of their own mouth, or their own heart? Suppose you refer these points to an excuse of the Creator, or to His comparison with Christ; then consider what would have happened if the Pharisees had replied to His question. Suppose their answer to have been, that John's baptism was "of men," they would have been immediately stoned to death. (Luke 20:6) Some Marcion, in rivalry to Marcion, would have stood up and said: O most excellent God; how different are his ways from the Creator's! Knowing that men would rush down headlong over it, He placed them actually on the very precipice. For thus do men treat of the Creator respecting His law of the tree. But John's baptism was "from heaven." "Why, therefore," asks Christ, "did ye not believe him?" (Luke 20:5) He therefore who had wished men to believe John, purposing to censure them because they had not believed him, belonged to Him whose sacrament John was administering. But, at any rate, when He actually met their refusal to say what they thought, with such reprisals as, "Neither tell I you by what authority I do these things," (Luke 20:8) He returned evil for evil!
Note: the Marcionite version more closely resemble Matthew 21:25 than Luke 20:4, as it is the Pharisees rather than the Chief Priests, Scribes and Elders who challenge Jesus' authority.
The key point here, ignoring Tertullian's polemics, as he twists his commentary to place false motive in the Marcionite position, is that this passage goes to the very heart of the authority of Jesus himself. For the baptism in question is none other than Jesus' by the hand of John. The authority then is that which is conveyed upon Jesus, whether from heaven or merely mundane, obtained from men (compare Paul's claim in Galatians 1:1). Where this not referring to the baptism scene then there would be no need for this passage in the gospel, as Jesus would not care and would refute John, per Marcionite theology as belonging to the creator angel and not to God of the heavens. This is thus an element leftover from the source, not Marcionite.
We see this knowledge of John's baptism scene reinforced in the passage of Luke 7:16-28. Markus Vinzent rightly points out the sequence refuting John actually begins with the resurrection of the widow's only son at Nain (Luke 7:11-17), when the crowd witnessing the miracle proclaims, "A great prophet (Προφήτης μέγας) is risen up among us, and God hath visited His people." This Προφήτης μέγας is a clear reference to the role of John in the Baptism of Jesus, fulfilling Malachi 4:5. If not that then at the least it betrays knowledge of the theology and the need to counter it.
When John hears about Jesus' healing at Nain, to emphasize that they never met, John (from prison in the Marcionite account) sends his own disciples to ask Jesus, "Are you he who is to come, or shall we look for another?" [1] If John had baptized Jesus this would be a nonsensical question to ask. John would have seen the spirit descend on Jesus and would have remembered his proclaiming him the one. The Marcionite author placed this here deliberately to debunk the baptism, and to debunk the notion that John ever met Jesus.
The Marcionite writer then takes apart the elements of the Baptism scene and puts them on their head. First he has Jesus turn to the crowd and ask them "What did you go out into the wilderness (εἰς τὴν ἔρημον) to behold ?" (ἔρημος, compare, Matthew 3:1, 5; Mark 1:4-5), which of course is John. But he insults John by saying they would only see a weak reed blown around by the wind, not a strong staff of power. This same imagery it found in the OT insulting the rod of power of the Pharaoh (Ezekiel 29:6, 2 Kings 18:21 / Isaiah 36:6). The question is repeated,"But what did you go out to see?" (Luke 7:25) but this time the garments of John in the baptism story (Mark 1:6 / Matthew 3:5) are in view and coming under criticism, saying they are fine and soft for a king's palace (Herod's house I'd guess; more a house arrest of a VIP than a dungeon), not for roughing it outdoors.
The next verse (Luke 7:26-27) the question is asked a third time, "What then did you go out to see?" The follow reply of Jesus,"A prophet? Yes, I tell you, and more than a prophet. This is he of whom it is written, 'Behold, I send my messenger before thy face, who shall prepare thy way before thee.'" The comparison is clear for Mark 1:2 which speaks of John, saying "as it is written (γέγραπται)," and then quotes Malachi 3:1. [2] This is of course the prophet Elijah (means "my God is YHWH") come again (e.g., Malachi 4:5) which is fully understood by the Marcionite author. But he ranks
The passage closes with Jesus declaring, "I tell you, among those born of women none is greater than John; yet he who is least in the kingdom of God is greater than he." (Luke 7:28, AM 4.18.8). Parsing this we can see that as elsewhere the Marcionite author juxtaposes John against Jesus. While Jesus descends into Capernaum, presumably coming directly from the heavens, John came into being more naturally, "born of women," which by inference Jesus was not. Further, with the Malachi prophecy, specifically Malachi 3:1, 4:4-5 in immediate view, John is Elijah come again, the greatest prophet (Προφήτης μέγας) of the Jewish God. But even the greatest of the God of Moses' prophets he is less than the least Christian in heaven. [3] And he becomes aware of his inferiority in the Marcionite account after word of Jesus being a great prophet reaches him, and scandalizes him, leading Jesus to say 'Blessed is he who is not be offended (σκανδαλισθῇ) in me,' (Luke 7:23), directed at John according to both Tertullian (AM 4.18.5) and Epiphanius (P 42.11.6.8).
The point here is the entire passage is a deliberate theological counter was derived from the Baptism story, with all the elements including John's imprisonment (Mark 1:14) found in the Mark's version. Even the words chosen show contact.
Mark could not have created/invented the Baptism story if the prior Marcionite gospel is already countering it element by element. The story was already extent. I argue further that the story was in the prototype used by the Marcionite author as a base, and that he simple dropped the opening verses (well reworked them in a counterpoint theological incident), but in a way where their original presence can be detected from references dependent upon the lost elements. In reality only four of the first twenty verses of Mark got "dropped" or were not addressed. [4]
This is why I say you are wrong. The internal evidence of the Marcionite gospel leaves strong evidence against your position.
Disagreeing with your conclusions, and being able to present a case, does not make one a Papist. I'd be far more careful than to try and label people who question your claims as one thing or the other in order to dismiss them without addressing the evidence. Very poor logic.
Notes:
[1] Dialogue Admantius adds that John is in prison when he makes this request, mirroring text found in Matthew 11:2-3 over that found in Luke 7:18-21. IMO Matthew seems to preserve the original text, Luke has been redacted, and in a pedantic manner.
[2] It is my view that Mark conflates two prototypes, one with an opening like in Matthew quoting Isaiah and one with an unnamed quote from Malachi, but Mark assumes is also Isaiah.
[3] This is the point of the rich man and Lazarus story of Luke 16:19-31, where a man rich in Moses is less than the poorest of Christians (Lazarus).
[4] The four missing verses not addressed are 1:1 (IMO simply versification of the prototype gospel's title), 1:3 quote of Isaiah (from the other prototype version used by Matthew, not the one used by Marcionite/Lukan author; Mark conflates both), and the temptation in 1:13-14. The Baptism scene and the description of John are addressed in chapter 7:16-28 about John, and in the question of authority in Luke 20:1-8.
