Christians care because to us if you don't believe in God you are going to, as MinecraftNerd says, to the Nether (Hell). We believe heaven is real. That, if you accept Jesus Christ into your heart and ask for forgiveness, you will go to heaven. We don't want our friends, family, and basically everyone to go to a horrible, fiery, awful place.
In the US, we have the First Amendment . We have freedom of religion. You can believe what you want. Just realize why we are doing it .
