A second marcionite threat perceived by "Mark" (editor) in Mcn figures clearly in the episode of the calling of the Pillars.
The original text of Mcn 5:1-11 is the following:
But it happened that the crowd pressed upon him and heard the word of God. And when he was standing beside Lake Gennesaret, there he saw two boats lying by the lake. But the fishermen had gone out of them and washed their nets. He entered into one of the boats which belonged to Simon and asked him to put out a little way from the shore; he sat down in the boat and taught the crowds. But when he had finished speaking, he said to Simon, "Put out into the deep water and let down your nets for a catch!" But Simon answered, saying to him, "Teacher, we have toiled all night long but caught nothing. But I will not disobey your word". And immediately they threw out their nets and enclosed such an amount of fish that their nets were tearing. And they waved to their partners in the other boat to come and to help them. And they came and filled both boats, so that they almost sank. But Simon fell down at his feet, saying, "Please! Go away from me, for I am a sinful man, Lord!" For amazement had seized him about the catch of fish they had taken. But his partners were James and John, the sons of Zebedee. But he said to them, "Come on! You are no longer fishermen of fish, for I will make you fishermen of people!" But when they heard that, they left everything on the shore behind and followed him.
The brutum factum signaled by Klinghardt is that "Mark" (editor) divided this episode, by placing the calling of the Pillars in the beginning and especially separating it from the miracle of the miracolous cath of fish.
Klinghardt doesn't reveal (still) the theological reason, however I can see easily it.
In Mcn, the calling of the Pillars appears clearly to be a coincidential event: if Jesus was not pressed by the crown all around him, then he would have had no need of a boat and hence of the Pillars. They are useful only insofar Jesus wants to be separated ("a little way from the shore") from the crowd around him. This may allegorize the need of a hierarchy to rule the crowd. Even so, even if evidently separated from the crowd (and in this fact there is apparently his privilege), that hierarchy has to remember that his mission is to conquer further new crowd (=the "fish").
"Mark" (editor) didn't like this marginal role of the Pillars, their being chosen only in function of the need of ruling the growing number of Christian proselites.
By having made the calling of the Pillars an isolated episode, "Mark" (editor) made their calling an imperscrutable act of the divine will, and not more contingent and relative to the caprices of the crowd and the mere "technical" need of Jesus (as it appears clearly in Mcn).
Being chosen by the imperscrutable divine will, the anti-marcionite motif becomes clearer: the Pillars don't derive their power by being casually separated from the crowd around them in virtue of a mere technical contingency (their being found fortuitely by Jesus on a boat), the Pillars derive their power by being divinely separated from their families in virtue of a pure divine caprice.
Now they are predestined in their role of fishermen (just as Paul was predestined to be apostle), not more coincidentially chosen as such.
Thanks to Mark's corruption of Mcn, now Marcion can't say more: "Alas! You Pillars had been chosen only to help Jesus to evangelize the gentiles, not because you were predestined from the birth as my Paul was".