Rusra02, you are assuming everyone decides to follow a Christian doctrine (which one?) globally making everyone the same. Of course, if everyone was the same and like minded regardless of what religion you choose, there will be world peace. No debate there. That could mean everyone practices the tenants of Satanism. Same thing. There would be peace if everyone followed Satanism.
Building on your comment. What do you mean when you say "truly follow the Bible? I need to understand how you believe in God. Do you believe Jesus is God? Do you believe in a Trinity? Do you believe Jesus and God are two separate entities? That makes a difference in how you view or read the Bible.
For example, if you believe that Jesus is God, you'd have to also believe then that the Laws and cruelty in the Old Testament were commanded by Jesus. If not, then you can get a by on the Old Testament and talk about how Jesus returned to save man kind from God's wrath and the Bible's idea of sin.
If there is one true God, and I believe there is only one, it stands to reason there is but "one faith". (Ephesians 4:4-6) I do not believe the Bible teaches that God is a trinity. Rather, I believe Jehovah is the true God, and Jesus Christ is his Son. (John 17:3) What laws mentioned in the Hebrew Scriptures do you view as cruel or unjust?