1. Write books. Finish series. Get world at your feet and become richer than the Queen.
2. THEN tell the world the Harry Potter books are partially based on Christian tradition.
3. Within a week, also tell the world that Dumbledore is gay.
4. Congratulations! You have now shaved off the anti-Christian loonies in one step, and the anti-gay loonies in the other, while leaving your calm centrist base to float on the waves with big amused grins on our faces.
5. On the other hand, maybe with step 3 you got some of those Christian fundamentalists to rethink their avoidance of the books--only to cause them, in step 4, to go right back to slapping the Harry Potter series atop the Banned Books list. Or, vice-versa: maybe you piqued some gays' interests, but once they hear about the Christian thing, they aren't going to read them after all.
6. However, I bet you did actually gain a bunch of fans in both communities, since there's a lot of cross-tolerance that the media and general public don't often notice.
7. Not that it matters how many fans you gain or lose, as you are already richer than the Queen, and even if your next venture only sells half as many books as HP, you will still outsell all other living authors.
8. You get to edit and veto the movie scripts? Damn. Most novelists never, ever get that privilege. I want to be you when I grow up.