I would say that a blashphemer of the holy spirit is someone who hates God and everything good that God stands for. A lot of atheists are more against religion and hypocritical religious people, religious leaders who are greedy that con ignorant followers out of their money and live like millions while claiming to spend the money on poor starving children aroound the world, religious leaders that abuse children sexually, mentally, emotionlly and physically, perhaps while performing "exorcisms", who lie to people to get their money, false prophets like Harold Camping that make up dates when the rapture will take place, make up prophecies not found in the Bible and gain followers that give them their life savings believing they are great Christian profits of God. What about polygamists in the west who control and dominate their many wives and children, never elt them have the freedom ordinary American enjoy? Muslim imans that encourage terrorism, violence, oppresion and cruelty toward women, all these religious leaders, cult leaders, perhaps they are the true blashphemers.
There are atheist that hate the idea of a good, loving fatherly god who cares for his creation like they are his children. They refuse to beliee in a creator and say the Bible is a book of fairytales. There are pagans that claim the God of the bible is oppressive cruel, tyrannical harsh, demanding, his laws are unfair and oppressive, he does not give us freedom and Yahweh doe not offer true free will because if you go against him he will sentence you to burn in hell for all eternity.
To commit blasphemy not only would someone hate god but they would hate Jesus Christ and the Holy Spirit too, and they would love the Devil, the spirit of evil. Most people are too spiritually ignorant of who God really is and how evil, twisted and deceiving Satan is and how much Satan wants to destroy them and devour their soul, and how desperatly God wants to save them, to comit true blasphemy of the Holy Spirit.