When I was a kid, I was travelling for some reason with my Dad and his best friend. Possibly they both brought their whole families along, I really cannot now recall the context of the trip. At any rate, they got into a really energetic argument over whether or not there is a unforgivable sin named in the Bible, and if so what it might be. As best as I can now recall, one of them vigorously defended the view that a particular sort of blasphemy is a divinely condemned thoughtcrime (or perhaps spoken offense) which God will never forgive, while the other man maintained that all synoptic references to an unforgivable sin were not really about blasphemy per se but were rather about the total rejection of the Christian gospel.
This apologetic has a certain appeal, because it is difficult to imagine anyone but a confirmed apostate taking excessive joy in blaspheming the most obscure third of the Christian Trinity. That said, the crimes of blasphemy and apostasy have always been listed and punished separately, both in Jewish tradition and in Christian catechisms. The apologetical attempt to cleave them together into a single unforgiveable sin seems hamfisted at best.
Moreover, if the universe is such that there is only one word or deed or state of belief that will earn someone irrevocable eternal damnation, surely a loving deity would make it abundantly clear to his beloved creations what exactly that might be. The fact of widespread confusion on this issue, a confusion that I first encountered so many years ago, militates against the position that an all-powerful being actually wants everyone to be saved.