Examples?
You are right to say that one is often obligated by other moral precepts (especially charity) to perform a particular action, and this may sometimes include lying. The point is that this does not stop lying from being wrong - it’s right there in the Decalogue, it’s natural law. But sometimes it may be right to do a wrong.
Example: After the Nazis took the Netherlands, they sent SS to the home of everyone to flush-out Jews hiding with Gentile families.
Imagine three stormtroopers, armed with machineguns, going door to door in your neighborhood.
They come to a row of townhouses. Each of the townhouses has Jews hiding in the walls.
Mr. and Mrs. Smith are approached by the Nazis first, as Mr. and Mrs. Jones and Mr. and Mrs. Doe watch from their front doors.
The stormtroopers ask, “Do you have any Jews hiding in there somewhere?”
Mr. Smith, to avoid the sin of lying because you convinced the Smith’s that lying is always a sin and therefore always offensive to God, keeps silent. Mrs. Smith changes the subject for the same reason.
Unsatisfied with the answers, two stormtroopers enter. One stays behind to keep an eye on the Jones’ and the Doe’s. Machinegun shots are heard. The stormtroopers drag-out 4 bloodied bodies of Jewish children found hiding in the walls. Mr. and Mrs. Smith are lined-up against their house and executed with machinegun fire.
Next, it’s the Jones’ turn.
The stormtroopers ask, “Do you have any Jews hiding in there somewhere?”
The Jones resolve to honor God by telling the full truth. “We will not lie! We are good Catholics. And, we are fans of AthanasiusOx. So, yes, we have Jews in there!”
Thoroughly satisfied with the answers, two stormtroopers enter. One stays behind to keep an eye on the Doe’s. Machinegun shots are heard. The stormtroopers drag-out 4 bloodied bodies of Jewish children found hiding in the walls. The commanding officer of the small unit, splattered with the children’s blood, says, “It is good for you to avoid sin in this way! You will go straight to Heaven!” And he smiles and shakes their hands.
Finally, it’s the Doe’s turn.
The stormtroopers ask, “Do you have any Jews hiding in there somewhere?”
Mr. Doe, filled with zeal, decides to tell the best lies he has ever told in his life.
“No, we don’t, friend. But our walls are filled with British, French, Americans and Russians! And we have Jewish cookies in our pantry, straight from the concentration camps! So, please, come in, shoot up our walls, and dine on some cookies!” Mr. and Mrs. Doe burst out laughing, and start urging the stormtroopers to come in. “Please, come in! We really do have dinner in the oven. Chicken! The best you’ve ever tasted! We put on extra when we heard that you were making the rounds!”
The SS, unused to such a warm welcome, and to such anti-Allied and antisemitic sentiments, relax, thank the Doe’s, and go on to the next house.
The 36 Jewish children in the walls of their attic are saved!
Now, tell us all here how God will view the Smith’s, the Jones’ and the Doe’s.