I like dlws92's response very much. It's gentle and it's honest. It's also respectful to all concerned.
The problem with any belief system, whether it be purple, green or Robin's egg blue, is that believers will often put their own spin on things.
I've yet to find a religion that I think is inherently bad but, since religion must be administered by humans, a great deal of damage can be done when people start believing things that the religion doesn't actually teach.