Blasphemy of the Holy Spirit is a specific thing Lets look at the veses where it was mentioned and read it in context.
Mark 3
22And the scribes who came down from Jerusalem said, "He has Beelzebub," and, "By the ruler of the demons He casts out demons."
23So He called them to Himself and said to them in parables: "How can Satan cast out Satan? 24If a kingdom is divided against itself, that kingdom cannot stand. 25And if a house is divided against itself, that house cannot stand. 26And if Satan has risen up against himself, and is divided, he cannot stand, but has an end. 27No one can enter a strong man's house and plunder his goods, unless he first binds the strong man. And then he will plunder his house. 28 "Assuredly, I say to you, all sins will be forgiven the sons of men, and whatever blasphemies they may utter; 29but he who blasphemes against the Holy Spirit never has forgiveness, but is subject to eternal condemnation"-- 30because they said, "He has an unclean spirit."
What did the scribes do? They said that the Holy Spirit that was with Jesus was "Beelzebub" They accused the Spirit of being a demon, (like calling God satan) that act is the sin of blasphemy of the Spirit. verse 30 refers to "they" they where the scribes in verse 22.
So if one pronounces that another person has a demon and that person actually is indwelled by the Holy Spirit then one has just accused the Holy Spirit of being a demon and has committed the sin that "never has forgiveness" and they are "subject to eternal condemnation".
All Praise The Ancient of Days