Lesson 1 We are not allowed to speak lashon hora about an entire group, EVEN when we do not specify the names of any individuals. It is considered lashon hora to speak negatively about national or religious groups of Jews: i.e. chassidim, American jews, sfardim, ashkenasim, misnagdim.
Lesson 2 We are not allowed to say anything derogatory about Klal Yisrael (the Jewish people) as a whole. i.e. Jews are so.... or Everybody does ...