Uncomfortable Idea: If atheists are wrong, according to some Christian beliefs, they will be tortured for all eternity.
A similar question is, "Is the Existence of Allah an Uncomfortable Idea to the Christian?" I would think so. Because according to the Qur'an, they are going to Hell.
They have certainly disbelieved who say, " Allah is the Messiah, the son of Mary" while the Messiah has said, "O Children of Israel, worship Allah, my Lord and your Lord." Indeed, he who associates others with Allah - Allah has forbidden him Paradise, and his refuge is the Fire. And there are not for the wrongdoers any helpers. Qur'an 5:72