Blurring the lines.

[Mister Agenda]

There is a very simple test to determine whether one is a Christian or not. 1st do the claim to be? 2nd do they follow the canonical teaching of Jesus Christ?

That's the made-up version of the test specifically designed to let certain denominations claim that certain other denominations are not actually Christians. My verson relies on the dictionary defintion of Christian.

Why are their requirements for atheism who has no rules, and no requirements for those who claim Christianity who does have rules?

There is A requirement for atheism (and theism), which is simply the definition. The definition of Christian is slightly more complex, but basically anyone who professes Christ and the value of his teaching is in the club.

You want it to be otherwise, solely for the authority you think it gives you to declare other denominations you disagree with 'not Christians'.

Now, Muslims aren't Christians. They too include the OT and NT but have an additional book on top. They think Jesus was a holy miracle-worker born of a virgin. However, they think he was a prophet sent from God, not actually the son of God or God incarnate. For this (actual) reason, Muslims are not Christians.