People are sinful and always look around for someone else to blame. The leadership should be steering away from that, but more often than not they used it for their own advantage.
Very true on that second point. Scape goats and common enemies make for a convenient distraction and make for a useful device in bringing people together for a common cause. It's a pretty gross tactic, but it's an effective one. However, this case is a little different, and I'll explain below...
It seems incredibly odd and naive to come to conclude that Jews killed Jesus therefore we should persecute jews, especially given the fact that all of the Christians in the beginning were Jews (at least until Cornelius is converted).
And yet, historically, that's the conclusion people came to - all over the christian world. It's also been that way since some of the earliest Christians in Christendom. It's an attitude that persisted for almost two thousand years, and it even manifested itself in great men like Martin Luther who authored "On the Jews and Their Lies."
Even after the inclusion of gentiles, the Jewish members remained Jewish and continued Jewish practices (which led to some clashes between the groups over circumcision).
That seems true enough to me. There are plenty of verses that come to mind that single out the Jews specifically, though. Paul, who was Jewish himself, authored some that have been later used to justify antisemitic acts upon them. 1 Thessalonians 2:14-16 would be one.
14For you, brothers and sisters,* became imitators of the churches of God in Christ Jesus that are in Judea, for you suffered the same things from your own compatriots as they did from the Jews, 15who killed both the Lord Jesus and the prophets,* and drove us out; they displease God and oppose everyone 16by hindering us from speaking to the Gentiles so that they may be saved. Thus they have constantly been filling up the measure of their sins; but God’s wrath has overtaken them at last.*
I doubt any of the early Christians would have blamed Jews for killing Jesus, the scriptures indicate one important fact: we crucified Jesus. Had we not sinned, his sacrifice would not be necessary.
That's actually not true. Here are some quotes from notable early Christians.
"If someone had killed your son. could you stand the sight of him or the sound of his greeting? Wouldn't you try to get away from him as if he were an evil demon; as if he were the Devil himself? The Jews killed the Son of your Master......... Will you so dishonor Him as to respect and cultivate His Murderers, the men who crucified Him?"
-John Chrysostum C. 390 CE (Who wrote Adversus Judaeos, which even the Nazi party used to justify their actions during their WW2 atrocities).
"For the circumcision according to the flesh; which is from Abraham, was given for a sign, that you may be separated from other nations and from us, and that you alone may suffer that which you now justly suffer, and that your land may be desolate and your cities burned with fire, and that strangers may eat your fruit in your; presence and not one of you may go up to Jerusalem."
-Justin Martyr C. 160 CE
"Why was the temple made desolate? Was it on account of the ancient fabrication of the calf? Or was it on account of the idolatry of the people? Was it for the blood of the prophets? Was it for the adultery and fornication of Israel? By no means, for in all these transgressions they always found pardon open to them. But it was because they killed the Son of their Benefactor, for He is coeternal with the Father."
-Hippolytus c. 220 CE
"It is because you killed Christ. It is became you stretched out your hand against the Lord. It is because you shed the precious blood, that there is now no restoration, no mercy anymore and no defense. Long ago your audacity was directed against servants, against Moses, Isaiah and Jeremiah. If there was wickedness then, as yet the wont of all crimes had not been dared. But now you have eclipsed everything in the past and through your madness against Christ, you have committed the ultimate transgression. This is why you are being punished worse now than in the past. . . . If this were not the case God would not have turned his back on you so completely. . . But if it appears that He has utterly abandoned you; it is evident from this anger and abandonment that He is showing even to the most shameless that the One who was murdered was not a common lawbreaker, but was the very Lawgiver Himself, and the Cause, present among us, of innumerable blessings. Thus you who sinned against Him are in a state of dishonor and disgrace, while we who worship Him, though we once were less honored than any of you [i.e., as gentile pagans), are now established through the grace of God in a more respected position than any of you and in greater honor."
-John Chrysostum C. 390 CE
Blaming the Jews thus becomes a way of blaming others people for our own failings. It is just sinful behaviour and it still exists today - 'Get rid of the immigrants and things will be better' or even 'get rid of Christianity and the world will be better.'
Antisemitism definitely has very Christian roots, and though I do agree that they have been made scapegoats in similar ways that you describe the above examples, that ire didn't come from nowhere. It was a phenomenon that happened in Christian corners of the world precisely because of the way they have been singled out since the very beginning - as Christ killers.
"Why should we pursue the enemies of the Christian faith in far and distant lands while vile blasphemers far worse than any Muslims, namely the Jews, who are not far away from us but who live in our midst, blaspheme, abuse, and trample on Christ and the Christian sacraments so freely and insolently and with impunity?"
This was written by the Benedictine abbot Peter the Venerable of Cluny in a letter to King Louis VII of France in reference to the Crusade and why they should just kill the Jews instead. There are plenty of writings from Jews who survived the horrors of those times inflicted upon them, as well.
"I shall speak out in the grief of my spirit before my small congregation.
I shall wail and lament; for the Almighty has dealt bitterly with me.
Be silent, hear my words and my prayer.
If only he would hear me.
The crusaders massed at the gateway
To blot out the name of his remnants.
Small children cried out to him with one voice:
"Hear, O Israel, the Lord is our God; the Lord is one"
This was a poem written in remembrance of a major massacre that happened in 1096. Here's another account showing the effects of PTSD left on these people...
"They inflicted heavy tortures upon him. And when they beheld his suffering, they defiled [baptized] him against his will, since the blows with which they had beaten him left him unconscious. Having regained consciousness, he returned three days later to Cologne. He entered his house and, after waiting but an hour, went to the Rhine and drowned himself in the river. About him and others like him Scripture states (Psalm 68:23), "I will bring back from the depths of the sea."
Had the Jews not been singled out in the bible like they had been, I have to wonder if they would have suffered such a terrible fate throughout history...