Criticising others is easy and, for many enjoyable. So it may be a pleasant surprise to learn that there is a mitzvah to rebuke wrongdoers (Leviticus 19:17). However, rebuking someone properly in a way that is helpful is very hard; the mitzvah is hedged around with qualifications and limitations about when and how to do it.
We should not try to rebuke others when there is no chance of the criticism being accepted. As the Talmud puts it, "Leave the Jews alone. Better that they should be sinners unknowingly (shogegin) than be wilful sinners (meizidin)" (Beitzah 30a). If the attempted correction is likely to elicit a hostile reaction or to entrench the wrongdoer in his ways, then it is better not given.
As the Talmud puts it, "Just as there is a mitzvah to say something that will be accepted, so there is a mitzvah for a person not to say something that will not be accepted" (Yevamot 65b). Rebuking should be done, if at all, gently, humbly and not self-righteously.