And that is where the contention lies.
There are two aspects of 'justification'. The aspect Paul addresses, and the aspect James addresses. No one disagrees on the aspect of justification that Paul addresses - becoming righteous in God's sight. The contention lies on whether or not literal sabbath keeping is among the deeds that James says justify a person. We know from Galatians that it is not. But it's not a hill worth dying for...unless a person keeps a literal sabbath to the exclusion of and in ignorance of the works that really do justify a person. That is the danger of the sabbath keeping argument. And as far as that danger goes, I'm of the opinion you just alert someone to that danger and then you just let them do with it what they will.
It's so commonplace that these discussions endlessly go in circles. And do you know why they do that? It's because the dishonest parties refuse to acknowledge when they've been corrected accurately with scripture.
Here's how this next part would go if I cared to go through the multiple exchanges of it:
GEN: Ferris, why is it that we are still expected by God, on penalty of damnation, not to murder?
Ferris: Because we are to obey the 2 Commandments of Jesus.
GEN: Yes and what are those Commandments, Ferris?
Ferris: To love God with all your heart, mind and strength and love your neighbor as yourself.
GEN: Yes, Ferris, that's correct. And can you tell me how it is that God has told us to love Him?
Ferris: Well, I can, but I won't.
GEN: That's ok, Ferris. I'll tell you. He has told us through His first 4 Commandments how He expects mankind to love Him. He never decided that He didn't want us to stop loving Him in those ways, just as He never decided He wanted us to stop loving mankind in the ways that the 5th thru 10th Commandments make clear.
And there you have it. Once again. The reason it makes zero sense that God still expects ALL 10 Commandments to be obeyed EXCEPT the 4th.
He only ever blessed and sanctified ONE day of the week. Genesis 2:2-3
He only ever called ONE day of the week HIS Holy Day - the Holy of the Lord. Isaiah 58:13
God doesn't change and everything He has EVER blessed, sanctified or made Holy is still Holy to this very day.
ETA: God tells people to take their shoes off when they are standing upon Holy Ground. The Seventh Day is a Holy Day. Do you show reverence or respect for the day that God has made Holy? Or do you blaspheme it endlessly, demanding that nobody make a big deal out of the ONE day that God has declared a
Holy day to Him? Do you love the things God loves and hate the things God hates?