I find it fairly simple. I would rather know the truth than live in delusion, personally. Myself. I don't see where the implication is to destroy someone else's beliefs. Only to modify your own accordingly in light of truth.

It's hubris to believe in a single ascertained truth (yours) and thus invalidate and dictate another's truth.

If you are an atheist and your friend is not, the truth is that you disagree. Their truth is a God exists. This should not destroy your friendship, but if it is so fragile that it does, it's better the irreconcilable relationship ends.