I don't recollect John the Baptist or anyone else claiming John had faith in Jesus before he was born...
John leaped for joy, according to Elisabeth...But was that because of Mary's voice, or being filled with the Holy Spirit???
And why did John leap for joy??? Was that because of Mary's presence, or a sign to Elisabeth???
If babies are born with faith in Jesus, apparently millions of kids lose that faith while they grow into teens and adulthood...
And in some place on earth, Jesus is unknown to the people (except for babies ???) who somehow lose that knowledge as they grow???
Justification is another matter...We are all justified by the sacrifice of the life of Jesus...We are all given grace, freely...