Here's my take on Blasphemy against the Holy Spirit. I do not consider it FINAL impenitence but INITIAL impenitence. In coming to the Faith and to Baptism, the Holy Spirit leads the soul naturally, through actual graces, to recognize the "motives of credibility" that God has revealed Himself in Christ and in the Church. That's what these Pharisees were doing, rejecting the notion that all the things they saw Our Lord do and teach backed up His credibility as the Messiah. Consequently, this rejection of these INITIAL impulses from the Holy Spirit prevent a soul from coming to the faith, into the Church, and to the Sacrament of Baptism. As the Council of Trent taught, the impulses leading souls into the Church and toward initial justification come from the Holy Spirit.