Our Gemara on amud Beis discusses the principle of אין מעבירין על מצות we do not pass over a mitzvah.  This matter has many halackhic implications as how one must behave if he enters into contact with one mitzvah opportunity, despite wanting to stop and do another, even greater mitzvah.  An excellent summary of the halachos can be found in Chayye Odom 68.  However, today I would like to discuss an opposite concept, brought down in a Teshuva of the Radbaz 1479-1573 (#187).  What about when there are two potential sins that require corrective action, do you pass over the minor sin and focus on the major, or vice versa:

The Radbaz deals with an interesting question:

There was a group of rebellious individuals, whom the rabbinic authorities considered that if they came down hard on them and punished them, they might become apostates and leave the community altogether.  Yet, to remain passive would be a de facto, giving permission to sin, or at least imply that the sins were not as bad as they were.  This would be a distortion of the Torah.

Radbaz rules that they must aggressively repress the sinful activity, no matter what it would lead to, even if the individuals abandon faith altogether.  He paraphrases our Gemara and states: אין מעבירין על עבירות “We do not pass over a sin”. The implication is even if a greater sin might come about, we tend to the violation in front of us.  He goes on to say, that the principle of “All Jews are responsible for one another’s mitzvos” does not apply to apostates.  

Radbaz does conclude with a cautionary note:

The leader of the generation has to be moderate in such things, according to which not all people are equal and not all transgressions are equal. If the transgressor seems to have little regard for the Torah and is arrogant, then we should enforce the law, despite what he may do.  His actions are not on us.  However, if the transgressor seems to be open to change, then we should engage him and draw him close, hoping that little by little, he will change.  There is no hurry to punish him, lest it leads to mishap.  These matters must be decided according to the eyes of the Dayan, so long as all his actions are for heaven's sake (and not motivated by personal bias or ego.)

Another fascinating discussion about rebuke, hate and the sinner can be found in Tosafos (Pesachim 113b) who draws a distinction between moderate hatred and utter hatred, maintaining that the state of utter hatred should be avoided even for the bona fide sinner.

However, we know that times have changed.  In practice, we do not usually come down harshly on sinners, almost regardless of the circumstance.  Here is one final source, that is perhaps the most lenient.  This comes from a loyal student of Rav Chaim Volozhin, in the name of his master (כתר ראש אות קמג)

תוכחה - שלא לדבר קשות, ודברים קשים אינן נשמעין, רק יאמר בלשון רכה ואם אין טבעו בשום אופן לדבר רכות, פטור הוא מלהוכיח.

Regarding the obligation to rebuke - there is an obligation not to speak harshly. For harsh words are never really heard.  One must only use gentle language.  Should a person not be of the personality to speak in this gentle manner, he is exempt from the mitzvah of rebuke.