Moshiach, the Rebbe says, that if we look at the cause of the destruction of the Beis Hamikdosh (holy temple) and we then fix the cause of exile, we will have God rebuild the Beis Hamikidosh and regather all Jews from exile to redemption.
What is the cause of our long bitter exile, the cause is nothing more, though of course nothing less, then brotherly hatred.
At the time the Temple was destroyed, all Jews were on a very high spiritual level, unlike when the first Temple, where the sins that caused the destruction was idolatry, giliu arayous, and murder.
For those horrible crimes, 70 years of hell sufficed to cleanse their souls and we find they did not revert to such foolishness, rather were on a high spiritual level.
They still did not have the brotherly love required of a spiritual people.
Now this is most interesting, if you think of it.
How can worshipers of God, on high spiritual levels, actually have enmity?!
Does it make sense?
All the angels in heaven only love one another, as we say in our prayers, that they first allow another to praise GOD, their sole activity at times, for they know that love precedes all!?
The answer is most enlightening.
You see, it is precisely their spiritual level that prevented them from loving others or at least contributed to their rationalization of why they need not love another.
You see, if someone has no spirituality whatsoever, hopefully it should be obvious that all men are created equal, but if someone is spiritual, it is very easy to begin to delude oneself, not that, one must love all people rather that, “I am greater than you.”
Now the sins of idolatry etc. are revealed sins. If I am God forbid worshiping an idol, it is obvious that I am doing something wrong, however if I believe that you are a cow and I am a Divine incarnate of some saint or something, I don’t really think that I am doing something wrong, merely stating the fact.
In fact, there was a great Rabbi, leader of many Jews who focused much attention on having Jewish people not speak ill of each other.
Coming to the leader of Jewry in his times, the Rebbe Rashab, wishing for an approbation for his book, the Rebbe Rashab did not give it, as he did not include, not thinking bad.
For to not do an action which is evil is not as difficult as in your own heart of hearts, thinking, seeing, feeling, good, love, towards your fellow Jews.