The Pharisees heard that Jesus was gaining and baptizing more disciples than John although in fact it was not Jesus who baptized but his disciples.
So the Jews were lying when they tried to make John jealous. The Devil always was the father of lies.
Lying is almost universally condemned in Scripture. "Thou shalt not bear false witness." Yet there are circumstances when a lie is justified. We would surely not betray RAF pilots shot down over France to the Gestapo. Kant believed that it was always possible to avoid the outright lie by giving an oblique answer, but if the intention is still to deceive, where is the difference?
My own view is that some people by their actions have frittered away their right to be told the truth. Perhaps the best example in Scripture is Pharaoh who was asked by Moses to be just allowed to worship the Lord in the Desert when his real intention was to lead the Exodus from Egypt. Pharaoh by hardening his heart and stiffening his neck against the Lord's demands had sacrificed his right to the truth.
We often justify a lie by calling it a white lie when its purpose is to let someone down lightly rather than face the bleakness of the truth.
Do I look fat in this dress? There is no answer to that.