@davidrevoy What I find most offensive about this "request" is the idea that somehow it's a good thing for you to compromise your creative vision so that it's palatable for an audience you have no interest in catering to in the first place.
I'd be inclined to say something like "Thank you for your email, but I fear you are mistaken about the nature of your relationship to Pepper & Carrot. It is not intended for people who aren't comfortable sharing same-sex relationships with their children."