1. in God’s presence, sin cannot stay, it is destroyed.
2. Jesus in the womb was still Jesus Christ, Lord and God.
3. To protect the bearer of God, she had to be made filled with grace and she had to be made free of sin — for her to be able to bear the Lord
now her own parents being sinful did not affect this as mary is just a creature, and sinlessness being in contact with sinfulness does not affect sinlessness (e.g. a newborn baby in contact with a sinful mother), but the blazing power of God that destroys anything that is tainted with sin, if that is kept in a box/womb which has even a slight tain of sin, that box/womb will be destroyed.
~ by Cronos
The scriptures teach us the Lord Jesus walked among us, yet sin was not destroyed. In the Old Testament our Lord walked among us before the flood. Yet, once again, sin was not destroyed. And, as we find in Peter, Christ descended into hell. Surely if there is one place that sin exist it is in hell.
But the strongest evidence we have that premise 1 is flawed is simply that the Holy Spirit dwells inside every believer.
While I would agree with your 2nd premise, I find no scriptural support for your 3rd premise either.
As we can see by the scripture in premise 1, God has been in fact known to dwell among us even in our sinful nature. Clearly our Lord Jesus is an example of this, dwelling on earth with sin all around. He couldn't possibly have been tempted, now could he?
I would submit the whole reason of killing sin isn't the very presence of God. God appears numerous times to people without people dying. God's Holy Spirit indwelt David for David's anointed life-a period of which he plotted and murdered Uriah. Rather the method of killing sin was on Calvary's cross.
And while I appreciate Cronos' interpretation, there was no need for God to "protect the bearer of God" since God did and does in fact dwell among sinful creatures to reconcile us to Him. He did not need to "protect" a person from His wrath.
Rather He became our sin who knew no sin.