Sefer Chofetz Chaim Chapter 3 Halacha 1 footnote 1 (part 2)

Today we concluded with reading a little bit more of the introduction to Sefer Chofetz Chaim which we try to do around a fast. He mentioned that one of the reasons Lashon Hara is so prevalent is because the sources for these laws are spread out all throughout Shas and poskim and that is why he felt he must put everything together into one sefer with such detail and elaboration. This will allow those misinformed or not knowledgeable in the matter to have it at there fingertips and those that do know the Halacha can easily review in order to combat the yetzer hara, evil inclinations pull and excuses to speak lashon hara.

With that being said we saw today in even greater detail the same thing we have been seeing the past couple weeks that speaking lashon hara even if true, when the guy is right there in front of you is still forbidden. When Rebbe Yossi in Erechin seems to say it’s permissible, Tosfos says is only a statement that doesn’t necessarily sound like lashon hara, meaning it can be understood two ways, positive or negative. 
According to the Sefer Yereim and Rabbeinu Yonah Rebbe Yossi was talking in situations where spreading the lashon hara will be beneficial for the victims or others to stay away or be careful for example spreading news of a thief, or an extortionist, or one who verbally or physically hurts others. Or if a person is known to purposefully transgress a sin that everyone knows is a problem and he was warned and doesn’t care about it then one can speak about that issue with others, for example if he or she eats non -kosher food like pig or shell fish. If you are willing to spread the news with the suspect in the crowd (barring the issue that he might go after you next) that is an indication you are talking about it for the sake of the truth and the honor of Hashem or to protect others and help the victim. Otherwise, if one is only willing to talk about the issue behind his or her back that is indicative that the person making the statement or spreading the news is doing it for personal reasons making him or herself look good in front of others while putting down other people, which is absolutely forbidden.

Bottom line if it is not constructive don’t say it whether in front of the person or behind his or her back.