The heresy of modernism, rampant today, is in its essence belief in universal salvation. Many of the modernists seem to be saying merely that most people are saved, but when questioned on this, finally admit that they really believe that everyone is saved. It all seems benevolent, except that it is the benevolence of Satan, the benevolence of disbelief in Christ. The vast majority of them are saying that there is even no Purgatory, that everyone on Earth, whatever he has done, repentant on not, steps from death straight into Heaven.
This is the benevolence which teaches that sin does not really count, and that God approves of all morality and of all immorality. It is the santification of worldliness.
The modernists can be seen to be divided into two wings: the left-wing modernists who teach that the Commandments themselves do not represent God's universal moral law, and the right-wing modernists who teach that the Ten Commandments are indeed God's universal law, but that all men, ultimately, are excused by the factors of ignorance, of weakness, or of faulty environment.
A second branch of the right-wing modernists, however, can be distinguished. Its adherents hold that the Commandments are valid universal laws, and also that long-term ignorance of wrongdoing in the breaking of the Commandments is impossible, and that weakness and environment similiarly are not excuses for long-term unrepentance. Where they reach their goal of belief in universal salvation is by saying that, well, everybody on Earth who is in long-term unrepentant sin will repent at the last moment, somehow or other.
Is this possible? It goes against what we see. Surprisingly few irreligious people come to religion on their deathbeds in any visible way. So, too, with sin of other kinds.In a sense,the longer the delay of repentance, the more unlikely it will be. But this is not a refutation. Refutation comes from the words of Christ, Himself. He often speaks about the reality that there will be people, many people, who will, in fact, find themselves damned. At The Judgment, the Son of Man "will place... the goats on His left." (Matt.25:33) If there shall be no goats at all at The Judgment, then this statement is a lie.
God, in the parable, said to the rich man, "Thou fool, this night your life will be demanded of you." (Luke 12:20) If the rich man was, after all, surely going to wake up in the middle of the night and repent, he would not be exactly a fool. The words of Christ would be ill-chosen, and fundamentally absurd.
Similiarly, and even more explicitly, Christ says: Many will try to enter but not be able." (Luke 15:24) After death, they shall find that they are fixed in a state of unrepentance, even though Heaven begins to look attractive to them.
"Those who have done evil shall rise to the resurrection of condemnation." (John 5:29) Notice that this is in St.John's Gospel, the mildest of the four Gospels. True Christianity does not include a wing of those believing in universal salvation.
"The Son of Man will send His angels, and they will collect out of His Kingdom all who cause others to sin and all evildoers. They will hurl them into the fiery furnace where there will be wailing and grinding of teeth." (Matt.13:41-42) If the angels go out and there is no one to collect, then Christ again is a liar.
It all fits together. Those who try to be more benevolent that Christ find themselves only advocating the benevolence of Satan, and this comes not from thin air, but from previous committment to sin of some kind. Those who humbly accept the mysteries of Christ, including the difficult ones, find themselves on the path that leads to repentance and to holiness.