Here is an interesting commentary given by Bart Erhman:
According to Tertullian, Marcion took the words of Jesus found
in Luke 6:43 quite seriously: “No good tree bears bad fruit, nor does
a bad tree bear good fruit, for each tree is known by its own fruit.”
Look around at this world we live in, said Marcion, this world of
poverty, starvation, disease, war, and death. What kind of God could
have created such a cesspool of misery and despair? In the Old
Testament, God himself declares, “I am the one who creates mis-
ery” (Isa. 45:7). If a tree is known by its fruits, and the Old Testament
God is one who produces misery, what does that say about God?
He is the one responsible for all human suffering. He cannot be
thought of as good.
But if there are good fruits there must also be a good God. This
according to Marcion, is the God of Jesus, who must therefore be
a different God from the one who created this evil world.
(Studies in the textual criticism of the New Testament, page 347, Bart Ehrman)