This is a dirty, abominable habit of petty-minded people. Almost all are victims of this dire malady. This has become an ingrained habit of narrow-hearted, mischievous people. This is a Tamo-Guna Vritti. The Lila of this world is kept up by this evil habit of man. It is Maya’s strong weapon to spread restlessness throughout the world. If you see four men sitting in a group, think that some backbiting is surely going on there. If you behold that four Sadhus are talking, you can at once infer without any shadow of doubt that they are backbiting against some person or other. The Sadhu will be talking: “The food of that Kshetra is very bad. That Swamiji is a very bad man.” Backbiting is more prevalent amongst the so-called Sadhus than amongst householders. Even educated Sannyasins and householders are not free from this dreadful disease. A real Sadhu who is engaged in contemplation will always be alone.
The root cause of backbiting is ignorance or jealousy. The backbiter wants to pull down or destroy the man who is in a prosperous condition by false vilification, slander, calumny, false accusation, etc. There is no other work for a backbiter except scandal-mongering. He lives on backbiting. He takes pleasure in backbiting and mischief-making. This is his Svabhava. Backbiters are a menace to society. They are worst criminals. They need capital punishment. Double-dealing, crookedness, diplomacy, chicanery, quibbling, tricks and artifices are the retinues of backbiting. A backbiter can never have a calm, peaceful mind. His mind is always planning or scheming in wrong directions. An aspirant should be absolutely free from this dreadful vice. He should walk alone, live alone, eat alone and meditate alone. If a man who has not removed jealousy, backbiting, hatred, pride, selfishness says, “I am meditating for six hours daily,” it is all nonsense. There is no hope of getting a meditative mood even for six minutes unless a man removes all these evil Vrittis and purifies his mind first by selfless service for six years.
(pgs. 192-193, Concentration and Meditation by Swami Sivananda)