I wouldn't say irrelevant.
As allonyoav, expert in Judaism since birth, said, ***As for people claiming that jews see the events in the Christian Scriptures as accurate- that is absolute nonsense. We see the Christian scriptures as a highly anti-Semitic, inaccurate document that completely misrepresents jews, Judaism and any events that may have happened.***
This means all Christians following their scriptures are anti-Semitic.
As Jeffrey, expert in Judaism since birth says, ***Is Christianity a sick religion, or not. YES it is!!
***
One can hardly conclude that non-Messianic Jews are totally indifferent when they feel Christian are either sick or anti-semitic for following their scriptures.
Another assumption is: ***Christianity falls apart without Judaism*** The question you would need to answer is, "Which Judaism?" The one described in the Tanach / Old Testament is completely different than the one practice today where the Talmud is practiced.
Yes, Christianity would fall apart if the Tanach was not a part of their Bible but no, modern Judaism would not fall apart if the Tanach was not a part of scriptures.
After Solomon's Temple was rebuilt, it was called Herod's Temple. The end of the era of the prophets had ended and so the Jews could/can no longer hear the voice of God. Had they been able to hear and follow God's voice, they wouldn't have failed in their revolt against Rome which lead to:
1. The destruction the Herod's Temple, the Holy of holies and the Mercy seat
2. The ability to have sacrifices or priests in the line of Aaron measuring up to the standard found in Ezra. (and no DNA samples of Aaron)
3. The ability to have a messiah in the line of David.
Therefore, modern Judaism has been able to find a way to exist without hearing the voice of God or being Torah observant. In fact, there are Atheist Jews because monotheism and the scriptures don't produce a "conflict that one might expect to find." (cat's meow)
On the other hand, Christian are the continuation of the Tanach. Hebrews 9: ***11When Christ came as high priest of the good things that are already here,[b] he went through the greater and more perfect tabernacle that is not man-made, that is to say, not a part of this creation. 12He did not enter by means of the blood of goats and calves; but he entered the Most Holy Place once for all by his own blood, having obtained eternal redemption. 13The blood of goats and bulls and the ashes of a heifer sprinkled on those who are ceremonially unclean sanctify them so that they are outwardly clean. 14How much more, then, will the blood of Christ, who through the eternal Spirit offered himself unblemished to God, cleanse our consciences from acts that lead to death,[c] so that we may serve the living God!
15For this reason Christ is the mediator of a new covenant, that those who are called may receive the promised eternal inheritance—now that he has died as a ransom to set them free from the sins committed under the first covenant.
16In the case of a will,[d] it is necessary to prove the death of the one who made it, 17because a will is in force only when somebody has died; it never takes effect while the one who made it is living. 18This is why even the first covenant was not put into effect without blood. 19When Moses had proclaimed every commandment of the law to all the people, he took the blood of calves, together with water, scarlet wool and branches of hyssop, and sprinkled the scroll and all the people. 20He said, "This is the blood of the covenant, which God has commanded you to keep."[e] 21In the same way, he sprinkled with the blood both the tabernacle and everything used in its ceremonies. 22In fact, the law requires that nearly everything be cleansed with blood, and without the shedding of blood there is no forgiveness.
23It was necessary, then, for the copies of the heavenly things to be purified with these sacrifices, but the heavenly things themselves with better sacrifices than these. 24For Christ did not enter a man-made sanctuary that was only a copy of the true one; he entered heaven itself, now to appear for us in God's presence. 25Nor did he enter heaven to offer himself again and again, the way the high priest enters the Most Holy Place every year with blood that is not his own. 26Then Christ would have had to suffer many times since the creation of the world. But now he has appeared once for all at the end of the ages to do away with sin by the sacrifice of himself. 27Just as man is destined to die once, and after that to face judgment, 28so Christ was sacrificed once to take away the sins of many people; and he will appear a second time, not to bear sin, but to bring salvation to those who are waiting for him.***
http://www.biblegateway.com/passage/?search=hebrews%209;&version=31;
The Jews who can hear the voice of God without being discredited pray that those who say that they can't hear the voice of their Creator (who made their brains, mouths, and ears) pay attention to the words God is speaking to them.
Therefore, as non-Messianic Jews have more in common with Atheists than those that are
mono-theists
believe in the Messiah
worship in a Temple
have particapated in the sacrifice that allows them to stand before the throne of God
as well as include the Tanach as their scripture
then Christianity would not fall apart if this sect of Judaism didn't exist.
Hope this helps