Self evident means it’s not opinion.
Self-evident means the conclusion is inherent to the thing in itself, derived through the use of pure logic—in this case, the thing in itself is Christianity.
Just because someone proclaims something to be self-evident doesn’t mean it is. If it were, it wouldn’t have taken thousands of years to identify. Remember, that which the Founding Fathers were declaring self-evident WASN’T Christianity. It was the idea that man has this list of rights.