147:
I may be on my way out now, (too many, much too many suspicions) but your comment caught me.
Your question is a real valid one, in my humble opinion not phrased respectfully towards the Shivtei Kah.
Let me try to answer. In their opinion, when removing him from their midst, they were doing a Mitzvah. What it was – that’s discussed by varoius seforim. But their act was not a wild act of anger, violence, or the like. It was an act proceeded with calculation and decisiveness, in their minds and conscience it was the proper thing to do. So much so, that after they had him in a holding cell (pit) they made a seudah, similar to a seudas mitzvah. They ate with out any guilty conscience, because that was the right and proper action to take. Such was their assumption all those years.
Only when faced before Yosef, and having the full truth shown to them ever so clearly, did they realize the enormity of their error. That is why ?? ?????, an expression more to mean “shaken”. When the truth flew at their face, contrast to their thinking og twenty two years, they were shaken.
So yes, a mistake had been done. “Leitzonim & bad”? No. No evil intent.