The truth is that they were all guilty of a far more blame worthy sin and it is that sin that God was now uncovering and for which he was exacting vengeance for their own good. This is stated in a strange way in the story. After the brothers tear their clothes in grief and anxiety and return together to Egypt, notice what Judah says to the prime minister here in verse 16
Judah already viewed things as if the sentence of slavery had already been instituted. As far as they were concerned they were slaves right then and there. He presented a strange combination here, our innocence and our guilt. How can both properly be spoken in one sentence? The answer is that the words accurately and pointedly describe the situation. They were innocent of the theft of Joesph's cup, but they were also deeply and irrevocably guilty of the dreadful sin of having sold their brother into slavery and this was now brought forcefully to life. No one could deny it.
Joseph may have imagined their self-serving excuses and eventual arguments that could follow, but there is nothing in the story to indicate that his brothers reacted in that way. On the contrary, there is reason to believe that the brothers were thoroughly changed men. That the self-sacrificing and humble spirit Judah showed in pleading for Benjamin as recorded in chapter 44 was true of them all.
This is the brothers talking to Joseph. They deeply sense their guilt, and were not at all inclined to excuse themselves, either now or later. They had labored under a burden of guilt for decades, and they were not about to come under its malevolent influence again, willingly.
