Yet, curiously to me, there seems to be a dynamic that seems to have been lost on most commentaries - at least the ones I've seen so far. And that is in THIS scenario, the brother's attack on Joseph was a DIRECT [as opposed to an indirect] slap at Ya'akov.
Permit me to expound
Joseph KNEW his brothers hated him, and so how did he go with alacrity to look for them? What made Joseph risk his own safety.
It seems that he felt compelled by Yaakov's instructions. This takes on several aspects
A. Due to Kibbud Av
B. Joseph probably was relying upon "sh'luchei Mitzvah einan nizaqin"
Thus both Yaakov and Joseph had expectations that no harm would befall Joseph despite the enmity of the brothers - because he was an agent of Yaakov himself. And yet harm happened anyway or at least Yaakov was so led to understand.
Let's illustrate some plausible contrasting scenarios
1 Let's say Joseph had actually gone on his OWN accord to check up upon his brothers. And add to that, the tattle-tale nature of Joseph, and the probability that he would blow the whistle back to Father. Then, the brothers might have felt justifiable provocation in manhandling Joseph when seen as a threat.
2 Let's say the brothers had "ASKED first and shot later" and then inquired:
"Joseph what are YOU doing here?"
And then had Joseph answered "Dad, sent me, otherwise I would be minding my own business".
Then, conceivably, the brothers MIGHT not have molested him - out of respect to Yaakov, NOT necessarily out of love for Joseph.
Joseph in this scene really IS an agent of Yaakov, but the brothers ignore that. As such we now see
A. They in fact struck a blow not just at Jospeh but also at their own father's agent!
B because they neglected to discern how Joseph came about catching up them they probably took it the wrong way
Shloymie: so what's the difference?
Let's see. Later on, Yaakov grows mistrustful - even paranoid? - about sending Benjamin. Where is his bitachon? Well, since Joseph was perceived to have been previously killed during his sh'lichut, Yaakov had unfortunately "learned" to lose his trust!
But of course, Joseph DID survive and actually DID thrive so he was NOT really "Nizzaq"! [Well he did suffer as a slave but we digress...].
Had Yaakov KNOWN that Joseph was merely MISSING but not seriously harmed, his angst might have been different. He might have had faith that Joseph was really OK and that he - viz. Yaakov - was merely punished by being deprived of Joseph's company. And he might have understood this as simple payback for having left HIS father Yitzhak!
He might have suffered but not to the point of "VAYMO'EIN L'HITNACHEIM". He might have been sad, but not depressed.
Tangentially we see these dynamics in the two reactions from the brothers
Reuben who merely wishes to return Joseph. His concern is NOT brotherly love, but concern for his Father
Judah, seems not concerned about Yaakov's feelings , but did have some mercy on Joseph as a brother.
Thus, the two dynamics are dealt with separately by the responses of Reuben and Judah.