Hi Nathan,
You write, "Bill erroneously states that sinless = no need for a Redeemer. Mary was sinless, but still needed a redeemer."
When Christ was nailed to the cross and died, the sin debt for all people was nailed to the cross with Him (Colossians 2:14). Christ died to pay our sin debt and to make salvation available to all who, by grace, through faith (Ephesians 2:8), will believe and receive His "paid in full" pardon from sin. That is why He is called our Redeemer; He came to redeem us from sin.
If Mary had no sin, if she were born sinless and remained sinless -- she would have no need for a Redeemer. And, being sinless, she could have died for our sins instead of having Christ incarnated as the Man/God.
If ANY human was born sinless -- that person could have done what Christ did -- die for our sins.
However, since the ONLY sinless person ever born, or who will ever be born, is Jesus Christ -- ONLY He could die for our sins.
How can you expect anyone to take the Roman Catholic church seriously -- when, from the Vatican down -- you teach such unBiblical doctrines?
If it not in the 66 -- it is not of God!
God bless, have a wonderful, blessed day,
Bill