The Passuk calls Yehoshua: א ישִאֲ שֶ רִרוּח ִבוִִֹ פנחס ִכז ִיח a person with Ruach (spirit) in him, and Chazal explain that this means he was able to deal with all types of people. Chazal tells us that in his younger years, Yehoshua went through a lot (with difficulty in learning). Perhaps this is why he became a leader, since he had experienced his own pain, and therefore he understood others.
One of the most famous letters of the Rambam, is called Iggeres HaShmad. It was written in response to the rampant persecution of the times, when many Jews were forced to convert to Islam, while privately they remained practicing Jews. These Jews approached a certain Adam Gadol, hoping he would be supportive of them, since at least they kept Yiddishkeit in secret, despite outwardly confessing to Islam. Alas, he was very harsh on them, and was unsympathetic. As a result, many were Mya'esh of doing any kind of Teshuva, and lost interest in Yiddishkeit altogether.
At that time, the Rambam was less than 30 years old, and he was not yet a known figure. Yet, he came out in the most critical way against this Adam Gadol, and he saved those unfortunate Jews by understanding them. He was upset with this Rav, since the Rav himself lived unharmed in a different part of the world, and had never suffered the same Tzaros and difficulties that these Jews underwent.
Such a person cannot judge such people. He simply doesn’t understand them. When we hear a Mussar Shmuess that’s not really for us, we need to remember: It’s no Mitzva to “commit suicide” by putting ourselves down, without understanding our own selves, and not realizing where we’re coming from.
They say that in Olam HaBah, people will be judged by a Bais Din who is their “type” and their generation; or else we would be in lots of trouble, Chas V'shalom. Perhaps the reason why the Rambam became one of the greatest leaders Klal Yisroel ever had ("מ ִשִֶמִֹהִע דִשִֶמִֹהִל ִֹאִק ִםִכ ִשִֶמִֹה") was because he understood people and sympathized with them, instead of criticizing. Notice how in Hilchos Teshuva he is extremely encouraging to a Baal Teshuva, and he elaborates loads. He insists that a Baal Teshuva is the most loved and precious person! P.S. The reason for Sin'as Chinam (and the Churban) is because people don’t work on understanding others who are different than them, whether in temperament, or in their Minhagim, or their Derech, etc.
