Obviously not because the intent and the message behind those words would be clear. They would be choosing those words because they want to discriminate against

Obviously not because the intent and the message behind those words would be clear. They would be choosing those words because they want to discriminate against non-believers by branding them as inferior. There is no good faith argument to be had in why a religion would choose "heathen" as a description of a non-believer unless they mean it in a negative way. The message itself is clearly bad and the chosen language reflects it. That's not the same as me calling a pregnant person a "pregnant woman" or someone else calling them a "uterus having pregnant person". The meaning in both cases is a biological female human who is carrying a baby in pregnancy. You can find people who will get offended by either phrase, but why? I don't get it. Neither phrase is meant to be disparaging or trivializing towards other people. If you hear "pregnant woman" you should assume that "woman" is meant in a biological sense and not a gender sense.