No, Matthew 12:31–32 does not speak of blasphemy against the Holy Spirit as the sin that cannot be forgiven to make people afraid of an exception to God’s grace. Rather, this passage calls us not to miss God’s unique way of deliverance from sin—through Jesus. It warns us not to persist in a life of blasphemy against God, which is what blasphemy against the Holy Spirit is. Missing the baptism by the Spirit means becoming like chaff that is burned with an unquenchable fire, as John the Baptist threatened. Christ, however, is gathering a people for God—even some from the blaspheming Pharisees, as will be shown in Matthew 12:33–37.
No, when Matthew 12:31–32 speaks of the blasphemy against the Holy Spirit as the sin that cannot be forgiven, this is not meant to make people anxious by suggesting some exception to God’s grace. Rather, this passage calls everyone not to bypass God’s unique way of deliverance from sin—namely, through Jesus. It warns us not to persist in a life of blasphemy against God, which is what blasphemy against the Holy Spirit entails. Christ, however, is in the process of gathering a people for God, and that includes even some from the blaspheming Pharisees. This much will become evident in what follows in Matthew 12:33–37.
Matthew 12:31 does not describe an exception to forgiveness that believers might stumble into, but stresses that there is only one way by which all sins can be forgiven. Missing that way means missing the remission of sins that God offers. Missing the baptism by the Spirit means becoming like chaff that is burned with an unquenchable fire, as was threatened by John the Baptist.1
31 Therefore I tell you, every sin and blasphemy will be forgiven people, but the blasphemy against the Spirit will not be forgiven.