I find the concept that the Talmud introduces today so difficult to understand. We are told several times in the Talmud that if we believe that ‘x‘ sinned (in this case Reuben and in others David HaMelech) we are mistaken.
This is difficult as the verses in the Torah seem to be pretty explicit. The get out in the Talmud is usually a convoluted argument where words in the Torah are changed around to save the innocence of the person in question.
I have similar issues with biographical sketches of great Rabbis who are painted in the most perfect terms and of whom it is impossible to imagine any tiny sin ever happened in their lives.
This point was beautifully articulated in the Edah Journal I read several years ago. The quote is looking at the question of how we evaluate a gadol in mondern times:-
“..we are engaged only with the last summation of their standing. We retell their path to wholeness while skipping over the internal struggle that permeated their soul. When we speak of our gedolim we get the impression that they appeared from the time they were created in their full stature…Everyone speaks, is excited and uses the Hafetz Hayim as a model for his purity of speech, but who knows of the wars, the struggles, the failures and steps backward that the Hafetz Hayim experienced in his struggle with the evil inclination?”
How are we to learn from gedolim, or indeed emulate them, if they are perfect and almost angelic. Their flaws make them human and make it possible for all of us to reach the highest levels humanly possible!
 Pachad Yitzchak, Igrot Uketavim: Mori V’rabi Harav Yitzchak Hutner, z’tl, p.217 quoted in Simcha Krause: Between the Yeshiva world and modern orthodoxy: The life and works of Rabbi Jehiel Jacob Weinberg, 1884-1966 By Marc B. Shapiro in Edah Journal 1:1/Marcheshvan 5761