Vayigash, Breishis 44:18. Vayigash eilov Yehuda.

Rashi says that the Vayigash of Yehuda was confrontational– he approached with a threat that if Yosef did not let Binyomin go, he and the brothers would attack and kill both Yosef and Pharaoh. Reb Elchonon asks, where was this brave and aggressive talk until now? Why were they so timid when they were accused of being spies and Shimon was imprisoned? 

Reb Elchonon answers, that when a person has yesurim, but he understands that these yesurim are coming because of a specific aveira, he must not struggle against the apparent cause of the yesurim, but should instead deal with it on a metaphysical level, by addressing the root cause of the yesurim through teshuva for the aveira, and be mekabel the yesurim with ahava. But when Binyomin was threatened, they realized that what they were experiencing could not stem from what they had done to Yosef, since Binyomin was not involved with the mechira, and there was no reason for him to suffer. (They thought that Binyomin was in danger; in truth, Binyomin would have been treated like a king when they left.) From what they saw, it was a threat to Binyamin’s welfare, so they decided that this episode could not have been a direct punishment for the mechira, and so they were justified- indeed, obligated- to use whatever means were in their power to defeat the threat, including violence. 

I saw a Ksav Sofer in Vayigash 45:28 that brings a Ramban that is exactly on point: the Ramban allegedly says that only suffering that comes 'behashgacha' is memareik an aveirah, but suffering that comes ‘bemikreh’ is not memareik. I’m not an expert in Ramban, but I have to say that the distinction between hashgacha and mikreh is perplexing, and I have not yet found such a Ramban. But if it exists, it supports Reb Elchonon’s vort. 

But I still think that Reb Elchonon’s vort needs work. People have, רחמנא ליצלן,  yesurim all the time, and it is impossible to know what they come from, and people go to doctors all the time, and according to most Rishonim, this is fine (see the machlokes as brought by R' Yaakov in Mishpotim, Shmos 21:19, Rak shivto yitein verapo yerapei, whether it's a reshus or a chiyuv.) 

But with the addition of R Berel Povarsky’s derech in his Bahd Kodesh here, it works better. He says that Yosef’s intention, and the Shvotim’s intention in their regret and guarding of Binyomin, was that once they realized that Yosef, as a Ben Rochel, was entitled to some malchus, they realized that the basis of their decision to get rid of Yosef for his attempt to achieve malchus was flawed, and so they needed to do Tshuvas Hamishkol. Mishkol means balance; Tshuvas Hamishkol is a specifically designed experience that has to speak directly to the aveirah. It has to balance the aveirah in all respects– it should counter balance the benefit from the aveirah, the enjoyment of the aveirah, and the chillul hashem of the aveirah. So until Binyomin was endangered, they decided that what they were experiencing could serve as a real tshuvas hamishkol, and they were mikabeil quietly. But once the circumstances showed ramifications that did not fit into that rubric, the Teshuvas Hamishkol concept no longer was valid, and so they were entitled to, and expected to, resist.