Why is the subject of interpersonal relations so weighty?
HaRav Chain of Volozhin is quoted in "Nefesh HaChaim" as saying, in the name of his master: "The Gaon of Vilna said: the main toil of a person must be focused on the sins between man and his fellow man in all of their fine points."
In order to understand how such a great person should regard even one sin against a fellow man, let us describe a point from a story of one of the giants of generations, HaRav Zalmale of Volozhin, brother of HaRav Chaim, one of the [spiritual] giants of his times.
As a young man of twenty, he already knew the entire Torah by heart! Once, when Rav Zalmale was sitting in the beis medrash, he was approached by a man who told him a chiddush which did not find favor with Rav Zalmale. He said: Your words are like fruit that is not tithed. Shortly afterwards, he regretted what he had said and went out to seek him in order to appease him, but couldn't find him.
Rav Zalmale had a wealthy father-in-law. He hired a man to seek that person throughout 365 botei medrash, but he was nowhere to be found. Rav Zalmale was so distressed that he became ill. His father-in-law saw the situation but was helpless. ]
Finally, he found someone who was willing to go to Rav Zalmale and 'confess' that he was the man but Rav Zalmale was not fooled, and his condition worsened. All this — because of a single act denigrating a fellow man!
Rav Zalmale went to the Vilna Gaon who said to him: When someone seeks to repent wholeheartedly, Hashem will see to it that the insulted person will forgive him. This declaration finally succeeded in reassuring him.
From this incident, we can learn an inkling of the importance of a sin towards a fellow man even if the slight was negligible and incidental.
Let me explain more fully. Loshon hora is a prohibited commandment, as is harmful gossip. The gemara says that everyone is guilty of transgressing the prohibition of "the dust [negligible] of loshon hora," and the Rambam, in his commentary on Mishnayos, maintains that everyone in actuality transgresses this prohibition.
Snide remarks enter this category and are very frequent and common. In fact, all the stumbling blocks of speech become second nature and are hard to shake off because they come so naturally and are so ingrained in a person that he 'excels' in them. He bears grudges, seeks revenge, and harbors animosity etc., all on a high level because it comes so naturally.
A person is capable of transgressing a whole gamut of actual lavim so long as he does not work hard on uprooting these negative habits and improving himself. It should be a life saving task and he must plot and plan how to get rid of negative traits and actions. This is especially imperative during this time of Sefira when we mourn the deaths of Rabbi Akiva's thousands of students who failed in this particular area.
It is vital to feel the significance and necessity of self-improvement in matters between man and fellow man. In 5708, when Bnei Brak was also being shelled, the Chazon Ish wrote his suggestion for salvation — to be careful in matters of deception.
Incidentally, the Chazon Ish also worked on fine-tuning his character on interpersonal matters even fundamentally to the degree that he said: in the same manner that I toiled in the subjects in the Talmud, so did I work upon myself in matters between man and his fellow man, not to hurt or grieve anyone.
I heard this from a firsthand account of a person who either heard it from the Chazon Ish in person or from one of his disciples.
Why, indeed, are people so sorely lacking in this area?
Why? Because the world is built on competition. There are places of Torah study which are built on scholastic success and progress, but this can also lead to ruination.
Scholastic competition, kinas sofrim, is a very mighty force. One who pushes himself to pass up his fellow student can truly achieve great things.
The danger therein lies when the competition is no longer a factor, when one fails in the race and others pass him up and he no longer has the push and incentive to continue to persevere in study and exert himself. He is out of the running. And then comes the crisis, a terrible catastrophe.
