True Christianity is one wherein the Christian believes that he is saved for eternal life by the work that Jesus did on the cross, and by His resurrection.
It might be difficult for a Muslim or a Hindu or a Buddhist who believes in Jesus this way. But if they believe in Jesus for salvation, they are true Christians.
Conversely, anybody who thinks he is a Christian, but doesn't believe in Jesus' salvation, is not really a Christian.
The world likes to lump all the people who say they are Christians together, no matter what they believe. But true Christianity doesn't work that way.
This is discussing Christianity not atheism.
This is OT.
OT
I was baptised by a priest who is allowed to benedict you from the Pope which is the vicary of Jesus Christ on Earth through Peter. Is like if I was baptised from Jesus Christ in person. It is like Jesus Christ in person "certified" that I am christian.
Who are you to say I'm not?!?
I may not believe in him, but the fact that I was baptised by him reassure me.
Thank You.
/OT
In order to continue talking about atheism, we are simply setting foundations when we talk about other religions.
Being baptized is great! It is baptized into faith in Jesus salvation. If you formally reject Jesus salvation, your baptism becomes useless except to keep you in good graces in the Church who can't see into your heart. Faith in Jesus salvation is what saves. Baptism exists to strengthen that faith. If the faith isn't there, the baptism doesn't have anything to strengthen. It is useless.