Well, we discover in Luke 1 that some HAVE kept “the law” perfectly”, which knocks the Christian argument out of the water!
Luke 1:5 In the days of Herod, King of Y'hudah, there was a cohen named Z'kharyah who belonged to the Aviyah division. His wife was a descendant of Aharon, and her name was Elisheva. 6 Both of them were righteous before God, observing all the mitzvot and ordinances of ADONAI blamelessly.
Luke didn't make fun of Z'kharyah and Elisheva, but yet many Christians today believe they have the right to!
Truth be told, YHWH doesn’t expect us to “keep the law perfectly.” If we did, our name would be Y’shua! Christians have totally misunderstood the meaning behind James 2, so let's read it in context:
James 2: 1. My Brothers, do not hold to the faith of the glory of our Master Y'shua the Mashiyach with double-minded hypocrisy. 2. For if there come into your assembly a man with rings of gold or splendid garments and there come in a poor man in ragged and stained garments; 3. and respect is shown to him who is clothed in splendid garments, and you say to him, Be honorably seated; while to the poor man, say, Stand way over there, or sit here (in low prostration) before my footstool; 4. are you not showing double mindedness among yourselves and becoming advocates of evil thoughts? 5. Hear, my beloved Brothers; has not Elohim chosen the poor of the world, the rich in faith, to be heirs in the Kingdom which Elohim has promised to them that love him? 6. But you have despised the poor man. Do not rich men exalt themselves over you and drag you before the tribunals?
7. Do they not hate that worthy Name,  which is invoked upon you? 8. And if in this you fulfill the Torah of Elohim, as it is written, You will love your neighbor as yourself, you will do well: 9. but if you have partiality towards persons, you commit sin; and you are convicted by Torah as breakers of Torah. 10. For he that will keep the whole Torah and yet fail in one aspect of it, is an enemy to the whole Torah. 11. For he who said, "You will not commit adultery," said also, "You will not kill." If then you commit no adultery, but you do murder, you have become a defiler of Torah. 12. So speak and so act as persons that are to be judged by the Torah of perfect freedom. 13. For judgment without mercy will be on him who has practiced no mercy: by mercy, you will be raised above judgment. 14. What is the use, my Brothers, if a man say, I have faith; and he has no works? Can his faith resurrect him?  15. Or if a brother or sister be naked, and destitute of daily food, 16. and one of you say to them, "Go in peace, warm yourselves, and be full;" and you do not give them the necessities of the body, what is the use?
17. So also faith alone, without works, is dead. 18. For a man may say, you have faith and I have works; show to me your faith that is without works and I will show to you my faith by my works. 19. You believe that there is one Elohim; you do well; the demons also believe and tremble. 20. Would you know, O weak man, that faith without works is dead? 21. Awraham our father, was not he justified by works in offering his son Yitz'chak upon the altar? 22. Do you realize that his faith aided his works, and that by the works his faith was rendered complete? 23. And the Scripture was fulfilled which says: Awraham believed in Elohim, and it was credited to him for righteousness and he was called the Friend of Elohim. 24. You see that by works a man is justified and not by faith alone. 25. So also Rahab the harlot, was she not justified by works when she entertained the spies and sent them forth by another way? 26. As the body without the spirit is dead, so faith without works is dead also. (AENT)
 The Name invoked upon you is YHWH.
 Literally "restore life", not "save" as often translated.
 Some theologians allege this teaching to be opposite of the Pauline Epistles, such as Galatians. The reality is that Paul was grossly misquoted whereas Ya'akov was not. Rav Shaul did not accept empty ritual devoid of proper spiritual focus. He was Torah Observant; he kept the Moedim (feast days), the Shabbat, and took one or more Nazirite vows; he fasted on Yom Kippur, ate "clean" food and lived a Set Apart life in Mashiyach Y'shua. The fact is that Romans 7:12 totally harmonizes Galatians with, and complements, Galatians and Ya'akov.
 The Hebrew word for a righteous soul = tsadiq; righteousness = tsedeq; justified = tsadaq; notice they are the same word. A soul without righteousness can never be "justified" regardless of what theologians claim. The original root word for justified relates to righteous action. However, mainstream Christianity teaches that a person is "justified" solely on the merits of belief in Y'shua, and that observing Torah is impossible.
Even in Ya'akov's (James) day, some individuals wanted cerebral belief to "justify" themselves, which is impossible. Y'shua's person (example) and Spirit is meant to literally be imparted into us; this must be evidenced by our actions, otherwise we do not belong to him. Theological, or cerebral "belief" without works, is dead religion; but active literal Faith comes to life in Mashiyach. Torah Observance/obedience is clear evidence that we have passed from death to life. See John 5:29, Matthew 7:23.
Unfortunately, the arguments are endless. Many Christians refuse to acknowledge there's more to God and the Bible than just "believing in Jesus" and they are willing to resort to vicious behavior and even character assassination to prove their point. Traditional Jews and their converts are resorting to the same thing, so it's a never-ending battle. Messianic believers are caught in the middle and all we can do is make sure we constantly cling to the WHOLE Truth. Fortunately Scripture tells us that those who hang on to the end will be saved....