The reason some countries still stone is because they are still living under Old Testament Law, (Moses Law, in the Jews case), the ten commandments. When Jesus came he did away with Moses Law, and declared the just shall live by faith through grace in Jesus Christ. That's why the Jews wouldn't accept him, he was changing the law.
If you check up on these countries you will see none of them believe Jesus is the Christ, as a nation that is. All countries have some believers, even Israel.
For verily I say unto you, Till heaven and earth pass, one jot or one tittle shall in no wise pass from the law, till all be fulfilled.
On 21 May 2008 that in Kenya a mob had burnt to death at least 11 people accused of witchcraft. They do so for religious reasons. They were Christian.