You shouldn’t have to do this, but you might have to regardless.

I’m 15 and an atheist.  My parents are Christian and found out. They threatened to kick me out. What do I do?

If you have nowhere else to go and no other place to stay, then publicly backtrack to them for your own safety, peace of mind, and security.

If you need to blow off steam or acknowledge your ideas, do it with friends you know won’t betray you to your parents. Lots of siblings and friends of QUILTBAG youth with bigoted parents exercise this very same survival strategy.

Privately think what you want until you have adult autonomy and financial security, whether that means higher education resulting in a degree / credentials / certification or employment.  Then you don’t have to worry about what they think because you’ll no longer be subject to their rules and regulations.

I won’t lie. These three years will be hell for you. Your parents shouldn’t make your safety or well-being contingent on adopting their belief system, but they are and they’ll probably be able to get away with it. Endure till you’re eighteen and then do what you want.

All the best.