Loving our Fellow as Ourself -- #1

With all the Achdus problems in the world, it is important to fortify ourselves with Mussar against strife, and so let us, B'Ezras Hashem, begin a short program of insights into the Mitzvah of 'Vi'ahavta li'reiacha kamocha' -- ('And you shall love your fellow as yourself'):  

#1:  Perhaps first and foremost, we must all understand that it is just as forbidden to do something mean to someone else as to, perhaps even break Shabbos or eat treif, Chas V'Shalom.  Because treating another Jew badly is a transgression of the Mitzvah to love our fellow as ourself -- which is just as much from the Torah as any other Mitzvah.