It is not much use trying to make judgments about Christians and non-Christians in the mass.
Mere Christianity – C. S. Lewis (1952)
It strikes me that this could be said about anything or any religion so even after reading the rest of the passage I am not too sure what point is trying to be made.
I suppose that there could be an element of everyone having the right to their choice as to faith and then within that belief their own interpretation of the teachings but, and this is where I am even more at a loss, then that is just the concept of free-will (maybe).
This brings to mind a couple of sayings. The first being, ‘That you can’t judge a book by the cover’ because all people are unique and therefore, it stands to reason that even those within the same religion have a different interpretation of the same teachings. This leads to the second saying … ‘It would be a boring world if we were all the same’.