Only a dim bulb would use this argument.
To be a Christian in good standing, all you have to do is accept Jesus Christ as your savior. Once you have done that you are then obligated to live a good life, learn more and abide by Christ's teachings.
It is not comparable to becoming a brain surgeon at all.
You can become a Christian in literally an instant. You don't have to earn a diploma.
A person using this argument would only be displayed the absence of any grasp of Christianity.
I've read something like that.
Now... just WHERE was it??..??
Jesus answered, The work of God is this: to believe in the one he has sent.
Here: read it in context... https://www.biblegateway.com/passage/?search=John+6&version=NIV