Lesson 1
As mentioned, it is considered lashon hora when we speak negatively of any sect/group of Jews. This includes saying things like "sfardim always..." or "oh those lubavitchers..." or "wow the Jews from that area are so..." This is something to be really careful about.
Lesson 2
The mere listening to lashon hora, even without believing it, is very harmful because it encourages the speaker to continue relating derogatory information.
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Lashon Hora = Saying a derogatory/negative statement about someone else that is TRUE
Motzi Shaim Ra (Defamation of Character) = Saying a derogatory statement that is FALSE
About Whom is it Forbidden to Speak Lashon Hora - Any Individual Jew - Alive or not, - adult or child, family member (spouse, in-laws, parent, child, siblings), groups/sects of Jews, Entire Jewish Nation