Righteous people can also change

Berachos (28b) The Sages taught: Shimon HaPakuli arranged the eighteen blessings, already extant during the period of the Great Assembly, before Rabban Gamliel, the Nasi of the Sanhedrin, in order in Yavne. Due to prevailing circumstances, there was a need to institute a new blessing directed against the heretics. Rabban Gamliel said to the Sages: Is there any person who knows to institute the blessing of the heretics, a blessing directed against the Sadducees? Shmuel HaKatan, who was one of the most pious men of that generation, stood and instituted it.

The next year, when Shmuel HaKatan served as the prayer leader, he forgot that blessing,

and scrutinized it, in an attempt to remember the blessing for two or three hours, and they did not remove him from serving as prayer leader.

Berachos (29aWhy did they not remove him? Didn’t Rav Yehuda say that Rav said: One who was serving as the prayer leader before the congregation and erred in reciting any of the blessings, they do not remove him from serving as the prayer leader. However, one who erred while reciting the blessing of the heretics they remove him, as we suspect that perhaps he is a heretic and intentionally omitted the blessing to avoid cursing himself. Why, then, did they not remove Shmuel HaKatan?

Shmuel HaKatan is different because he instituted this blessing and there is no suspicion of him.

Let us suspect that perhaps he reconsidered and, although he had been righteous, he had a change of heart? Abaye said: We learned through tradition that a good person does not become wicked.

And does he not become wicked? Isn’t it explicitly written: “And when the righteous one returns from his righteousness and does wicked like all of the abominations that the wicked one has done, will he live? All of the righteous deeds that he has done will not be remembered given the treachery that he has carried out, and in his sin that he has transgressed, for these he shall die” (Ezekiel 18:24)? Abaye responds: That verse refers to a righteous individual who was initially wicked and repented, but ultimately returned to his evil ways. However, one who is initially righteous does not become wicked.

And does he not become wicked? Didn’t we learn in a mishna: Do not be sure of yourself until the day you die, as Yoḥanan the High Priest served in the High Priesthood for eighty years and ultimately became a Sadducee. Even one who is outstanding in his righteousness can become a heretic.

Abaye responded: He is Yannai he is Yoḥanan. In other words, from its inception, the entire Hasmonean dynasty had the same positive attitude toward the Sadducees, and there was no distinction between Yoḥanan Hyrcanus and Alexander Yannai. Yoḥanan the High Priest had Sadducee leanings from the outset. Rava said: Yannai is distinct and Yoḥanan is distinct. They did not share the same position in this regard. Yannai was wicked from the outset and Yoḥanan was righteous from the outset. If so, it works out well according to Abaye’s opinion; however, according to Rava’s opinion, it is difficult. How could Yoḥanan, a righteous individual, have changed and turned wicked?

 Rava could have said to you: There is also room for concern that one who is righteous from the outset will perhaps reconsider and turn wicked, as was the case with Yoḥanan the High Priest. If so, the original question is difficult: Why did they not remove Shmuel HaKatan from serving as the prayer leader?

Sefer HaChinukh (523:2) It is from the roots of the commandment [that it is] since the impulse of a man's heart is evil, and sometimes a passion comes to his heart against his fellow; and even if he is an extremely proper man, he is not saved from sometimes sinning. And even if a man stands for [a very long time] upon the ways of righteousness, it is not impossible for him to overturn his thoughts and to become bad. As behold, they, may their memory be blessed, said (Berakhot 29a) that Yochanan served in the high priesthood and at the end [of his long tenure], he turned into a Saducee; [they also said about him that he was at first a true prophet, and at the end, he became a false prophet]. Hence the thing is fit to not rely upon the heart of a man to punish his fellow according to his testimony; and even if the convicted is a total evildoer and the most common of commoners and the one testifying is the greatest sage in Israel. But when those testifying are two fit men, there is an assumption about all of the seed of Israel that they will not agree to testify falsely. And [this type of] an assumption is [powerful] about all things.

We see the issue of R Greenblatt is in fact a dispute between Abaye and Rava and clearly the gemora accepts the view of Rava that a righteous individual can change and do something wrong