On the contrary, one of the effects of a belief in sin is to justify malevolence towards the sinner under the guise of a wish to bring him to repentance. When we get rid of the belief in sin, it becomes much harder to disguise our unkind feelings, under a cloak of morality. The morality of the heart, as I see it, consists in the main of kindly feelings and good nature. But these cannot be produced by sermons: they are produced by good digestion, sound glands, and fortunate circumstances.
Source: "On being edifying" [From: Mortals and Others: Bertrand Russell's American Essays, 1931-1935, v.1 (1975)]
More info.: https://russell-j.com/EDIFY.HTM