We find that Yosef’s brothers harboured animosity to him almost from the beginning:
וַיָּבֵא יוֹסֵף אֶת דִּבָּתָם רָעָה אֶל אֲבִיהֶם – And Yosef brought evil tales to their father. (37:2)
Rashi explains he brought three issues he brought to his fathers attention. The first was that Leah’s sons allegedly mistreated Bilhah and Zilpah’s sons for being “slaves”, the second was that he suspected them of illicit, adulterous relationships, and the third was that they ate limbs of live animals.
Rashi notes how Yosef suffered in each of these three areas later on in his life. Having accused his brothers of taunting and mistreating “slaves”, he was sold into slavery himself. Having accused his brothers of forbidden relationships, he was challenged by Potiphar’s wife in this area. For accusing them of eating live animals; when he was sold, they slaughtered a goat and dipped his coat into it, which they then presented to their father, implying his death. They then ate it.
R Ezra Hartman points out an issue with this. Regarding the adultery and slavery, Yosef was the subject of the challenges – they happened to him, presumably to learn that he was wrong in these areas. However, the blood his coat was dipped in did not directly involve Yosef at all. Given that these occurrences appear to be lessons, what was Yosef supposed to learn from it if it didn’t happen to him?
R Chaim Shmulevitz explains that sometimes, people cannot concede that they were wrong. It hurts too much to admit to someone else they were right all along. Yosef saw how he was wrong, and was forced to accept that what he had reported to his father was not true, and had to suffer in silence and indignity. His humiliation at seeing he was wrong was the lesson to be learnt.