''Son of man'' is the mere visible body (the psyche) of the man possessed by the pneuma, the Spirit of the Christ.
Jesus prophetizes that only the his visible body will suffer, but not the his Spirit, who therefore will abandon him on the cross just before the death.
Therefore the blasphemy against the Son of Man is allowed, but not so the blasphemy against the Christ (being an emanation from God).
It is strange (=unexpected, =improbable), under this hypothesis, that just the proto-catholic Matthew 12:32 has:
...differently from Mark 3:28, that sounds very 'catholic' insofar it hasn't ''son of man'' but ''sons of men'':Whoever speaks a word against the Son of Man will be forgiven, but whoever speaks against the Holy Spirit will not be forgiven, either in this age or in the age to come.
whereas Luke 12:10 is like Matthew:28 “Truly I tell you, sons of men will be forgiven for their sins and whatever blasphemies they utter; 29 but whoever blasphemes against the Holy Spirit can never have forgiveness, but is guilty of an eternal sin”—
The more probable explanation is that the verse is not so offensive to Catholics insofar it could stand not modified in Matthew and Luke.And everyone who speaks a word against the Son of Man will be forgiven; but whoever blasphemes against the Holy Spirit will not be forgiven.
But in Mark the verse had to be changed. The readers of Mark were gnostics.