I'm going to take a stab at explaining something about myself which really bothers me; based on R' Kluger's observation, I'm pretty sure others do it, too.
I hear about a tragedy on the news, let's say a shooting, and it hurts. But then I hear that the victim was in trouble himself, was involved with a gang maybe, and it hurts a little less. Take the collar bomb story from a while back, and the FBI's determination that the victim was in on the plot at the beginning – oh, then I guess that's not so bad.
Or a man comes to my door collecting for tzedakah, and he describes a heartrending situation. He has ten children, his wife is ill, his parents are ill, the family has great debt and he needs help to marry off his daughter. I can see his bad teeth. He has letters vouching for his authenticity. I want to cry, to pull out my wallet and give him whatever I have. But then I ask him what he does for a living, and the answer is that he sits and learns. Oh, wait a minute, some part of me says. Then I don't feel quite as sympathetic.
I could give many examples of practical wrongs or ethical wrongs or halachic wrongs we diagnose, consciously or subconsciously, as reasons for others' suffering: They built their homes near a volcano, they got involved with drugs, they opted not to go to college, and so on. They broke Shabbos, they engaged in illicit relations, they laundered money and defrauded the government.
These calculations are often correct, from a logical standpoint, but on some level they are a defense mechanism. They come to make me feel less guilty about not helping, to make me feel less guilty for putting these people out of my mind and going about my life.
This is what R' Shlomo Kluger (grandson of the more famous R' Shlomo Kluger) saw in the actions of the righteous people of Kfar Sakhnia, who did not mourn for Yerushalayim (Gittin 57a). Those righteous people identified, as the gemara (such as Shabbos 119a) does, the sins of Yerushalayim: Failure to rebuke, lack of shame, disrespect, failure to educate their children in Torah, and so on. They saw reasons for her suffering, and accepted the resultant devastation as Divine will.
And then they saw no reason to mourn - and this was, itself, a grave sin.
Finding explanations for our own suffering is appropriate, and if they reduce the pain then so much the better.
Finding explanations of the suffering of others, to understand a cause and effect, to educate myself about proper behavior, is an obligation of my religion.
But using those explanations to numb my sensitivity, to fail to feel their pain, to fail to go to them and embrace them and cry with them – that's just wrong.
חטא חטאה ירושלים, said Yirmiyah. Yerushalayim has sinned. Guilty! But I am obligated to cry and fast and sit on the floor and feel pain in her pain, nonetheless. Her pain must be my pain.
Please! May this be the last Tisha b'Av on which we mourn.