"Real chrstianity" (pro-Jewish Fundamentalist Protestantism) is only some three hundred to four hundred years old. Historical chrstianity is rabidly anti-Jewish.
Of course, if you're one of those dogmatists who hold that the "original chrstianity" became corrupt and had to be "restored" later (under Luther, Calvin, Smyth, Wesley, Campbell, Smith, Russell, Hensley, etc.) then you can't admit this.
God has always had a remnant of those who believed Him. This was and is true in Israel. This is true within Christendom.
Real Christianity is defined by what the Bible teaches which is a record of what Christ and the apostles taught and practiced (in the New Testament). From the very beginning there was the corruption you mentioned. Even during Christ’s earthly work there were enemies from within, particularly Judas. Later, there were many false teachers who attempted to hijack the movement whith their own ideas and teachings. This has gone on continuously since the beginning and is recorded in the New Testament.
Paul had to defend himself against the acusations you are bringing up... namely that he had rejected his Jewish heritage and that he hated Jewry.
Neither Paul nor Peter nor any of the apostles ever attemped to stir up war or persecution against the Jewish people. On the other hand Jewish leaders were constantly trying to murder them and wipe out the Christian movement. But it could not be stopped. These Jewish leaders went so far as to alter the Masoretic text to hide and conceal what was prophecied about Christ from the Jewish people. It was this constant attempt by Jewsish leaders to hang onto their power and influence that led them to attack Christ, His followers and ultimately led to the war in 70 A.D. that destroyed the temple and scattered the Jews from their promised homeland.
There has been a long history of false teaching in the name of Christ which blames Christianity for bad relations between Jews and Christians. For example, replacement theology teaches that the church replaced Israel and is entitled to the things promised to Israel. This is false and not based on the teachings of Christ or the apostles.
God has supernaturally preserved and protected His earthly people, the Jews. Yet this same God has repeatedly punished Israel from the days of Moses until now for her contually rebelling against Him. It is also this same God that has supernaturally protected and preserved a true remnant of believing Christians for the past two thousand years which, unlike the false gods which were exposed in Egypt during the Exodus, and the false gods of the Philistines and other enemies of the Jews which God destroyed, He has done no such thing to the God of the New Testament because He is the same God.
Moses believed God and spoke with Him face to face. The multitudes of Israel saw the manifestation of God’s glory in a cloud by day and fire by night. Many heard His voice like thunder. In spite of this and His great deliverance from the gods of Egypt, many did not believe and the desert is filled with their carcasses. Soon we will see this same visible glory of God in the sky again, but whether you believe is up to you.