All his life, Moshe pondered how and when he should rebuke the Jews. Ultimately, he learnt from his forefather Yaakov exactly how to accomplish this exceedingly sensitive task. He knew that he would have to rebuke them on his very last day. Devarim, from the root devorah, bee. Just as a bee dies after inflicting his sting, Moshe was to die after his rebuke. (Midrash)
Just as Moshe learnt the when to rebuke from his forefather, so did he learn the how. Moshe rebuked mostly in subtle hints, modeling Forefather Yaakov. Yaakov, in his rebuke, focused on the loss that was suffered as result of the sin. He also referred to the trait that caused the sin. (Reuven was rebuked and told that he would lose his rights to firstborn, kingship and priesthood. His hastiness was the focus of the rebuke, and not his action. Shimon and Levi, as well, were not chastised for their attack on Shechem, but for their having "stolen" the traits of Uncle Esav.) Moshe, also, related to the trait or cause, and not the sin itself. He drew attention to the loss–result. For this reason, he changed the sequence of his words, mentioning the sin of the Spies before the sin of the Golden Calf. This is because the result and loss for the sin of the Spies was greater.
R' A. L. Heiman zt"l, asked the following: the Torah stresses that Moshe spoke to all of Israel. Rashi brings the Sifri that Moshe was careful to include everyone to this "gathering of rebuke". If he would rebuke only a part of the nation, the others in the market place would later say to those who were present, "You heard the Son of Amram rebuking and you did not answer him?! Had we been there, we would have answered him back (Sifri: four or five times on each offense)! " So, Moshe made sure that everyone was there, saying, "Let anyone who has a way to defend himself from the rebuke and an answer to give do so now". This is hard to fathom. How could anyone defend himself to Moshe? Was someone going to refute the sin of the Spies or the sin of the Calf? Was someone going to deny the complaints voiced in the desert?
There is one answer that can be given to all the rebuke of Moshe. If you want to reprimand anyone for the sin of the Calf or the episode of the Spies, dig up our fathers' graves and reprimand them. What do we have to do with it? The truth of the matter is that by this time, all the people of the past were dead. If so, if the ones present were not those who sinned, why did Moshe reprove them? How could Moshe refute the defense of the "ones in the market place"? And, if they were, also, deserving of chastisement, why did his reproval relate to what their parents did and not for what they did themselves?
If one were to study the history of the Jews from after the sin of the Spies until Moshe's last day, he would find that the sons sinned the sins of the fathers. They also served idols (Peor), fought with Moshe about the Manna and lack of water, and they even tried going back to Egypt when faced by the war of Canaani, King of Arad. Instead of Moshe mentioning these sins directly, he addressed those of their fathers! He made it as if the sins of the sons are the responsibility of the fathers. And they, the sons, are responsible for going in their footsteps. But he did not focus on their own sins.
We have a lot to learn from this. At times, we look at our parents and are annoyed, noticing their mistakes and mishaps. Let us remember that these mistakes and mishaps may very well have some sort of déjà vu in our lives. And then, we should remember to be aware of our own weaknesses and to work on them.