Chazal call sefer Braishes “Sefer haYesharim,” the Book of the Just. A “yashar” is someone who doesn’t cheat, doesn’t steal, doesn’t act with malice – a straight shooter, a mentch. While I would take it as a compliment if someone described me as a yashar, when we are speaking about the Avos, points out the Netziv, it’s a bit of an understatement. Why don’t Chazal call it the Book of Tzadikim? The Book of Avos?
There is a collection of talks given by R’ Eli Sadan after the Rabin assassination in which he repeatedly quotes the answer of the Netziv: the Avos lived surrounded by idolaters and evil doers whose lifestyle and beliefs were diametrically opposed to everything the Avos stood for. The lifestyle of Sdom was an anathema to Avraham. Nonetheless, the Avos never lashed out with hatred and/or violence. To the contrary, we find Avraham praying for G-d to spare Sdom, Avraham extending hospitality to wandering idol worshippers, Avraham making a treaty with Avimelech, etc. They Avos treated everyone they came in contact with -- even those with whom they had profound disagreements -- with respect and dignity, with yashrus. That's an even harder challenge than having tzidkus in avodah.
When Bilam saw Klal Yisrael camped in the desert, he exclaimed, “Tamos nafshi mos yesharim” –- I want to be able to go to the grave like the yesharim of that nation. Bilam was “s’sum ha’ayin,” he certainly knew that he was not a real navi and did not have even a small percentage of the tzidkus of the Avos. He did not even have a hava amina that he could be like them in that way. But he thought al kol panim that at least he is a yashar, a mentch – he has derech eretz. However, when he saw Klal Yisrael and the mesorah of the Avos, he realized that even in this regard he was wrong. His conception of derech eretz was no match for the true yashrus that the Avos embodied.