To expand on orthonormal’s point, note impact bias. If you do end up having to be truthful with them, whatever consequences you’re imagining now are probably far worse that what you will actually go through. People tend to carry on just fine.
And remember that the virtue of honesty does not require telling all truths, but rather not communicating falsely. If telling your parents you are an atheist will mean to them that you are an amoral person, maybe you should not say so unless that is also true.
To expand on orthonormal’s point, note impact bias. If you do end up having to be truthful with them, whatever consequences you’re imagining now are probably far worse that what you will actually go through. People tend to carry on just fine.
And remember that the virtue of honesty does not require telling all truths, but rather not communicating falsely. If telling your parents you are an atheist will mean to them that you are an amoral person, maybe you should not say so unless that is also true.