Romans 3:23 since all have sinned and fall short of the glory of God,
Protestants like to use this verse to "prove" that Mary sinned. But is this a good defense on their part? Hardly. My point in this thread is not to argue about the Immaculate Conception, but to point out that protestants use of this verse and specifically the word "all" does not necessarily mean all.
Firstly, let's start out with some logic here. Do infants sin or children below the age of reason sin? Do the senile sin? Do mentally retarded persons sin? In some cases they may know they aren't supposed to do something, but do they have knowledge that it is a sin? If a three year old is hitting a brother and is told not to but does it anyway are they sinning? No, they might know that they are not supposed to do it, but they don't have knowledge that they are sinning. So by just using simple logic here we can see that these people are subtracted from the "all" in Romans 3:23. So "all" does not mean "all" in these cases.
Now lets use some scripture to see if "all" means "all". The problem with this is that the word 'ALL' here is the Greek word, 'PAS', which can have different meanings to the absolute that we immediately think of. Here are some scripture verses.
John 12:19 So the Pharisees said to one another, "See, this is getting us nowhere. Look how the whole world has gone after him!" This verse does not use the word "all" but the context is the same. "the whole world has gone after him." Really, did everyone in the whole world go after Christ?
Matthew 3:5-6 Then went out to him Jerusalem and all Judea and all the region about the Jordan, (6) and they were baptized by him in the river Jordan, confessing their sins. Really? Were all of Judea and all the region about the Jordan Baptized? Does "all" really mean all here?
Luke 2:1 In those days a decree went out from Caesar Augustus that all the world should be enrolled. Was everyone in the whole wide world enrolled or counted? Really?
Romans 11:26 and so all Israel will be saved; as it is written, "The Deliverer will come from Zion, he will banish ungodliness from Jacob"; Is this true, will everyone in Israel be saved? Really, every single person???
Romans 15:14 I myself am satisfied about you, my brethren, that you yourselves are full of goodness, filled with all knowledge, and able to instruct one another. Gee, I thought only God was filled with "all" knowledge. But according to protestant definition of the word "all", apparently every single one of us is filled with "all" knowledge.
The Greek word 'PAS' in many verses in Scripture simply means a 'great number', 'most of', or 'a lot'. So its appearance in the quoted passage can in no way be used as an objection to the sinlessness of the Virgin Mary.
As an added bonus, what did the founder of protestantism say about Mary on her state of sin? Let's take a look.
"It is a sweet and pious belief that the infusion of Mary's soul was effected without original sin; so that in the very infusion of her soul she was also purified from original sin and adorned with God's gifts, receiving a pure soul infused by God; thus from the first moment she began to live she was free from all sin."
Martin Luther: Sermon, 1527