This isn’t even remotely true.
And Jesus came up and spoke to them, saying, “All authority has been given to Me in heaven and on earth. Go therefore and make disciples of all the nations, baptizing them in the name of the Father and the Son and the Holy Spirit, teaching them to observe all that I commanded you; and lo, I am with you always, even to the end of the age.”
— Matthew 28:18-20
He has all authority, not just in heaven, but also on earth. And He’s using that authority right now. How do we know? He said because of that authority (therefore) we are to go into the world and make disciples of all nations, even the ones you don’t think He’s powerful enough to conquer. And we know we will be successful because He says He will be with us all the way to the end.
It’s just another way of saying what He said in Genesis 1 about subduing the earth and taking dominion.
No, saying someone isn’t a Christian is against the rules.