I mean, I've seen some pretty outrageous comments on this thread that would never be made about non-Judeo-Christian folk.
Calling anyone names is not helpful to anyone's salvation. Explaining what is sin and what is not is helpful to enable one to see the need for a savior. Lying to someone that sin is not sin is probably the larger sin because that one is deliberately causing another to turn from God and not receive the healing power that only God can bring.