The Apostle Paul thought he was doing everything right but, like other contemporaries of Jesus, he missed some of the biggest clues of what the Messiah would be like — welcoming toward other nations, for example. The 2nd half of Isaiah (chapter 40 to the end) has so much about God's new order, welcoming all the nations through the future Davidic leader (Messiah). The Jews of the 1st century were deeply bitter with Rome and fiercely nationalistic, causing them to miss this, and Paul was so focused on the Mosaic Law that he missed some of the glorious themes of the psalms and prophets which prefigured Jesus. Like Ebenezer Scrooge in A Christmas Carol, God gave him a special revelation, a conversion experience, because God knew his wrong path was out of ignorance rather than defiance against Him. Many atheists defy God, cursing His name and morals as a concept, because they can't get answers to their questions, but few people defy God with the knowledge that God truly exists. There are some, though, who are like that.
For instance, we should remember that when people use profanity it could be a combination of peer pressure, carelessness/thoughtlessness, and deep-seated anger. When Ted Turner, for example, made hostile remarks about Christianity, he expressed deep frustration and agony about how it wasn't able to help him in the past; many people miss this subtext when they hear angry statements such as the ones he made. Also, the harshness of his father needs to be remembered as an important factor in his spiritual state of mind, because we generally define our concept of God according to how our earthly parents, guardians, and mentors were. My main point is that there's a difference between ignorance and willful ignorance. Many people would believe if someone worked through issues with them, but many others don't see a need for it, or have already determined it's not an option, which is called willful ignorance. Sometimes willful ignorance comes through a lack of reflection on the beliefs that led to this point (Scrooge and the Apostle Paul/Saul of Tarsus). Sometimes it is because other deeper issues haven't been pinpointed and addressed.
The doctrine of "blasphemy of the Holy Spirit" has relevance in our Christian life because if it's basically calling evil good and good evil, then it's essentially a misconstrued understanding of morality, which we are all naturally prone to. (Isaiah 53 really means "all" when it says all of us like sheep have gone astray!) The opponents of Jesus thought Jesus was immoral to do good things on a Sabbath day, and that His miracles must have been Satan's way of deceiving people, so they had already rejected His heavenly agency based on how His philosophy was different. In John 9, they make the conclusion and then reject the evidence which goes against it. They conclude the man who was born blind and healed is not telling the truth, and rationalize it by saying he was born entirely in sin, so he has no right to talk back to them. They throw him out — even though, by saying he was born in sins which made him blind, they are admitting he used to be blind (but he isn't anymore!) and using illogical theology by saying a person who had a disability at birth was a worse sinner, even though he hadn't had a chance to sin yet when he was born!!!
I think of Stephen Hawking, the mathematician whose life's pursuit is in trying to figure out how the universe could come out of nothing, because he is convinced it could not have been created by God. Hugh Hefner, who founded Playboy magazine, rejected his Christian upbringing because he felt an inability to emotionally connect to his parents and was taught in psychology classes that strict codes of sexuality were the cause of this. Then, he was unable to make sense out of his fiancée cheating on him even though he had pushed her to have sex with him before marriage, based partly on how Hollywood's movies of the 30s and 40s had captured his heart and made him prone to self-indulgence. After a lifetime of developing a philosophy out of false interpretations of reality and creating his identity out of wealth and women, how possible is it for him to repent? Jesus said about the rich man who wouldn't change his priorities that it was as hard for a rich man to find God as for a camel to go through the eye of a needle. He then told His disciples that with God, it is possible. No one can explain why some people are able to change and others aren't, except just thank God for it and continue to pray for each other.
But isn't calling evil good and good evil, which is essentially what "blasphemy of the Holy Spirit" is, just as much a problem for Christians when they are averse to kindness and prone to anger, and then justify it on petty grounds? Frederick Douglass had very harsh words for America when it pretended to believe the Declaration of Independence's ideals but continued to condone human trafficking and physical and emotional abuse of slaves, and the North continued to profit in its textile mills off southern cotton. Would they have changed their business dealings if the atrocities in the South were as vividly described to them as the Nazi death camps are by Holocaust survivors and photos, or did they have a general idea that "some" abuse went on but stay intentionally ignorant? Sometimes I think the contemporary church is no better when it pretends to be caring but reacts with anger or aggressive Bible-thumping at honest questions or expressions of emotional pain.
I think a very hard, but very important, first step for Christians to make is to recognize that "the blasphemy of the Holy Spirit" hang-up which my questioner had is a problem they have but don't realize. The fear my questioner was going through is something most of us have: "How good do I have to be to avoid loss of His favor?" Invariably this becomes a quest to prove to ourselves with our deeds that we're pleasing God, and it becomes an obsession which we don't even realize is an obsession. I am thankful that I avoided having this at any point in my life, and I still marvel at that and don't know why I escaped it. All of us need to acknowledge that God does not place value on how much we accomplish, but on how gracious we are. His favor cannot be lost easily, and there are always warning signs when we are going down a bad path. It ultimately is on us to guard our hearts (Proverbs 4:23), but our goal should be to live freer lives and worry less about our own souls. We shouldn't put ourselves under the bondage of fear that God is only pleased with us if we do a bunch of things, but should instead live according to duty as an outgrowth of a pure heart, not the way to get a pure heart. It's hard to tell whether A Christmas Carol is more about grace or works, more Protestant or Catholic, in its view of repentance, but the main thing I identify with is that an awakened sense of duty to others is the result of his change. He doesn't choose to change to avoid hell, because he actually believes it's too late to change, but he becomes aware of how his father's anger rubbed off onto him and how his performance-driven ethic caused him to neglect the deep needs of others. Fear alone wouldn't have been able to change him, either; he needed the example of the righteous Cratchit family to show him that happiness is an outgrowth of virtue, and virtue comes out of a choice.