There seems to be some confusion about whether it's permitted to rebuke, and the right and wrong way to do it.
This is what Rebbe Nachman says in Likutey Moharan 2:8, about rebuking:
"Though rebuke is of great import, and all Jews are obligated to rebuke each other when seeing that the other is not behaving properly...nevertheless, not everyone is capable of rebuking.
"As Rabbi Akiva said. 'I wonder if there is anyone in this generation who is capable of rebuking' [Eruvin 16b]. And if Rabbi Akiva said this about his own generation, how much more so in our generation.
"When the rebuker is not capable of rebuking, then not only is his rebuke ineffective, but he is also causing a sense of malodorous repulsiveness in the souls hearing his rebuke."
Then, in the translation of the Kitzur Likutey Moharan, translated into English as 'Advice', by the Breslov Research Institute, we find the following, in the chapter on Moral Guidance, p 304:
"There is no contradiction between what was said earlier about the obligation which every Jew has to discuss spiritual matters with his friends, and the statement here that not everyone is fitted to give criticism.
"If you examine the different passages carefully, you will see that the idea that is applicable to everyone is having discussions with friends about spiritual matters: what is the purpose of life? What will remain of us, in the end? And so on.
"Even the simplest of people should discuss these things."
The Kitzur Likutey Moharan then continues:
"The kind of moral criticism which is referred to in the last passage is a completely different matter.
"It means making explicit reference to another person's sins, and saying to him: 'Why did you do such and such?' One should be very careful not to discuss people's sins and bad behavior with them, because one can weaken their soul through arousing this bad smell.
"The distinction between moral guidance and rebuke is implicit in Rashi's comments on the opening words of Deuteronomy, where he says that Moses did not rebuke the Children of Israel until immediately prior to his death."
So, go right ahead and rebuke if you are
a) on the spiritual level of Moshe Rabbenu
b) only going to do it once every 40 years.
Otherwise, Rabbenu seems to clearly be telling us to keep our mouths shut, and just stick to general discussions encouraging the people we know to think more about the spiritual aspects of life.
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