The simple truth is these people where calling a work of the Holy Spirit, an act of satans power.
Is that what they did? Looked to me like Jesus merely cautioned them against going too far down that path? Or at least, it could be interpreted that way. Jesus spoke and said that all blasphemy against The Father would be forgiven. He also clearly stated that blasphemy against him (the Son) would also be forgiven. Is it possible that in His abundant mercy, he Judged that even though it may sound like they were blaspheming the Holy Spirit (it did sound like that, no denying) he was also functioning even then as a Paraclete and Advocate and may have considered it a personal thing directed toward Him and hence forgivable.
The ultimate act of blasphemy against the Holy Spirit, is to me, still something that is seen through a glass darkly. The way that it shall be known is when "
they" (not the Pharisees in the time of The Christ) speak against the one promised to The Christ. He will return with fire in His eye. This we know. Why? What is the 'straw' that breaks the camel's back so-to-speak?
For this we turn to the "Test of Solomon" and consider the "child" and the two mothers. With an eye to the Reveal that belongs to The Christ, and was given to the Sent-One, John, also known as "The Beloved" - while looking at what is revealed about the "man-child" --we may consider what that "Test" of Solomon is about. There were two women. Both gave birth. One child died (was it smothered in bed?) and the distraught mother claimed that she was the rightful mother of the living child.
Solomon, in his famous judgment, was able to rightly show who the real mother is. Looking at this as prophecy we are given a clue regarding the nature of the blasphemy of the Holy Spirit. The Lamb of God is also the Bridegroom. The Saints of God are seen to be the "body of Christ" and the mystery that Paul spoke of, about the two joining in one flesh is known true. This is the purpose of God, that the Prayer that Jesus spoke, that we be "One with Him, even as He is One with the Father," shall come to pass. During this time, we know there will be those who come and fight against the Purpose of God. Jesus spoke much of this time and with many warnings, exhortations and revelations so that we are not surprised by the events that are designed to deceive (if such a thing were possible) even the elect.
When that one accuses those who belong to our Jesus, they are accusing the Holy Spirit in them. It will be then as it was in the time when the Lord Jesus first appeared on the earth. It will also be like the time of Noah. There will be many giving and taking in marriage. There will come one who declares that the "child" is rightly hers. We will no longer see through a glass darkly but shall see Him face to face and it will be with joy that those who are called and have been matured in Christ will remain in Christ, trusting Him to do what is right.