A better argument is to question why would his disciples go ever so far for something that may be untrue. They did sacrifice themselves - historical accounts confirm existence and crucifixion of Jesus and his disciples (as outlined within the Bible). From this, either of 2 things can be concluded:
- God is real and hence their sacrifices are validated
- God isn't real but to them God was, hence they sacrificed themselves for what they truly believed in
Make of it as you may. I'm neither atheist nor theist - I'm an agnostic but I do not shake away the possibility of God's existence.