Q. Does the issur of lashon hara apply to something that is public knowledge and that a person himself “shouts from the rooftops,” so to speak? For example, a person who constantly walks around in the street smoking wherever he goes, is it lashon hara to mention that he smokes?
A. A mentioned in question 2244 even when repeating facts well known by all there may be a prohibition of lashon haraa, as it still has to meet all the requirements that the Chofetz Chaim cites, to be able to further disclose in such a case, the information to others. (See Shemiras Haloshon klal 2), see also question.1554.
Rabbi A. Bartfeld as advised by Horav Shlomo Miller Shlit’a