Non believers can absolutely have an opinion on Bible interpretation. In fact one of Christianity’s flaws and what has led to its balkanization into innumerable denominations is the idea that only a central religious authority can interpret the Bible for application to daily living.

Also if anyone who says they’re Christian simply is one then that’s not really a true religious philosophy. It’s more a club with no real entry requirements.

There is one central belief in Christianity and it is that belief in Christ is the only path to salvation/heaven. A good person, the best person even, will go to hell if they have heard of but do not believe in Christ.

Christian doctrine has spread this message for millennia, and it and other derivative philosophical thought, has been used to justify countless atrocities around the world.

That should tell you or anyone reading most of why the world is the way it is today.