Premanand Maharaj Ji
Why is criticising others harmful to me?
Ninda gains nothing and costs merit
Criticising others gains nothing, and you carry the sin of the one criticised. Doing punya (merit) is very hard, and criticising a saint or devotee destroys it.
Criticising another gains you nothing, and you end up carrying the sin of the one you criticised to hell. Why should we commit that sin?