How Can Jesus Be Born Sinless if Mary Was Indeed Born a Sinner?

It's really wrong teaching to say that Mary was sinless. Romans 3:23 says that all have sinned and fall short of the glory of God. All people include Mary the mother of Jesus - no exceptions. Mary herself even admitted in Luke 1:47 declares that her soul rejoices in God her Savior. Then the dilemma comes in that for Mary to be sinless then she must have sinless ancestors. Roman Catholics, in due fairness, actually don't teach that Mary needed sinless ancestors. Roman Catholics even have this in their defense to say why Mary was born without sin even if her parents were sinners:

The blessed Virgin Mary to have been, from the first instant of her conception, by a singular grace and privilege of Almighty God, in view of the merits of Christ Jesus the Savior of Mankind, preserved free from all stain of original sin” (Pope Pius IX, Ineffabilis Deus, December 1854).

Roman Catholics teach that Mary was granted the special privilege to be conceived without sin by the grace and privilege of Almighty God. Then we reed this from the Catholic World Report in the article "Why I came to believe that Mary was conceived without sin":

Being that as it may, for many the root issue is the Catholic dogma of the Immaculate Conception, the teaching that the Blessed Virgin Mary was conceived without sin through the retroactive merits of Christ. The Church found the doctrine necessary, I think, for two fundamental reasons. First, Christ needs sinless human flesh, for he cannot be a sinner, and second, he must take his flesh from his mother really and truly if he is to be fully human. Indeed, the Eve-Mary typology iconographed in the image assumes Mary’s sinlessness, for she has to be in the prelapsarian (i.e., pre-fall) position of Eve to be able to undo what Eve did. She obeys freely, where Eve disobeyed, in parallel to Christ’s obedience undoing Adam’s disobedience (see Romans 5:12–19 and 1 Corinthians 15:21–22, 45–49).

This really starts to beg the question that Christ needs sinless human flesh for He can't be a sinner. Then they say that Mary was given that singular grace and privilege to be conceived without sin. Wait, didn't they just say that Mary was given that privilege to be conceived without sin yet her mother (who they say was named Anna) while Luke records her father as Heli? Luke 3 records the genealogy of Mary which goes pretty much backward back to Adam. What was amazing to know is that Mary herself fulfilled the seed of David part by being a biological descendant of David through Nathan. Joseph was a descendant of David through Solomon. So, Jesus was legally and biologically the seed of David via his legal father and his biological mother in the flesh. 

It doesn't become a problem for Jesus to be born sinless if Mary is a sinner for the reason that His Body was conceived by the Holy Spirit. If you read through Matthew 1 - you will notice that the genealogy of Jesus was legally speaking. He had no earthly biological father. Joseph was not his biological father in the flesh. Biologically, Mary was His mother in the flesh. Mary got pregnant by the Holy Ghost. If Roman Catholics can believe that Mary herself was spared from original sin by God's grace - why can't they believe that Jesus could still be born of Mary who was a sinner saved by grace and be sinless? Having no earthly father only a Heavenly Father, God the Father, and Jesus being God the Son from eternity past, could enter a sinner's womb, become human, and still be conceived without sin.

When we consider it - 2 Corinthians 5:21 says that He who knew no sin became sin for us. That refers to Jesus. The penalty of sin is death and Jesus paid for it by dying a horrible, criminal's death. Mary herself wasn't qualified to do so. Unfortunately, Roman Catholics have been unknowingly worshiping Mary and elevating her above God. It's so sad how some of them still continue to insist that Baptists and Protestants have been attacking Mary or maligning her. The sad truth is they are clinging to unscriptural beliefs about Mary. No, Mary won't crush the Devil's head - Jesus will. Jesus as God the Son even affirmed in John 8:48 that before Abraham, He was. That is Jesus is already God even before Mary was born. Jesus would be above Mary. David was Jesus' ancestor in the flesh via Mary but why don't Roman Catholics also venerate David but only Joseph, the legal father? 

As a Baptist, I believe Mary herself is a godly woman and a mother to model. I admire her example of offering two turtledoves as a sin offering. I admire how Mary pointed others to Jesus at the wedding of Cana. I love how Mary stood at the foot of the cross in so much reverence seeing Jesus no longer as her Son but as the Son of God. However, I'm against what Roman Catholics are teaching about Mary which isn't in the Bible. Unfortunately, some Roman Catholics will just continue to harden themselves even after the truth is explained as nicely as possible.