lightbrite: If your relationship is close enough that you feel you’re enabling the person, then chance are you may meet the three conditions. With people I know that I’m not close with at all that I see involved with self-destructive behavior, it may pain me to a degree that they are doing what they’re doing, but I recognize that giving tochacha simply won’t help the situation because it simply won’t be received.
You raise a good point with that, and I realize I have to clarify. If someone is bullying someone, humiliating someone, or hurting someone else, then it’s not a matter of the person hurting someone else, it’s a matter of someone being hurt. In such a case it would be a travesty for bullying or other such behavior (or even something as ‘minor’ as certain degrees of lashon hara) to be allowed to continue without interference, and a person standing by should stand up for what is right and protest such behavior, not in terms of tochacha, but as a means to protest interpersonal destructive behavior, not allow such a thing to continue, and to avoid hurting people.
There are things that are so horrible (speaking of other things) that someone has to, at a certain point, stand up and give an unequivocal no, not for the sake of tochacha, but to avoid, like you said, not standing up for justice (i.e. discussing inappropriate topics in a public setting). The problem with this is that it’s hard to draw the line about what should be protested and what shouldn’t, and it is often taken too far. One has to know, and if (s)he has a significant doubt if objections should be raised, they often shouldn’t.