When a person's religious conversation dwells on the faults of others' religions
“I think we may except [accept] it as a rule that whenever a person’s religious conversation dwells chiefly, or even frequently, on the faults of other people’s religions, he is in a bad condition.”
C. S. Lewis, letter to Mary Van Deusen, June 1952, p. 209 in v. 3 of the Collected Letters.