A midrashic theory of Anti-Semitism.
Anti-Semitism has been the bane of Jewish existence from the moment we had become a nation. The phenomenon of baseless hatred and unceasing hostility directed against one nation out of many is a striking one and many great minds have attempted to find explanations for it. It is not surprising then that the Sages of Midrash also had something to say about it.
The unique feature of anti-Semitism is that it is so unlike the familiar conflict between the nations, in which two national entities or ethnic groups struggle over land, resources or living space. Jews, on the contrary, have always been a peaceful and productive group in the lands of their dispersal and persecuting them works against national interest and harms their host nation, and yet is has not ceased to exist. This surprising and irrational feature of anti Jewish feeling is without parallel and has always been a source of amazement and bewilderment. In response, modern academic study of anti-Semitism attempts to separate it into different types, religious, political, ideological etc, and in this fashion, reduce and tackle this unique feature.
Classical Jewish sources contain attempts to understand anti-Semitism as a natural consequence of inter-national rivalry , same as nay other. This appears to be the import of Rashi's comments to Genesis 25, 22, "(Yakov and Eisav) were fighting and struggling for inheritance of two worlds". Others point out the role that religious separatism played in creating anti-Semitism; the nations dislike us because we refuse to assimilate to their ways. Ramban writes: … they did to us all kinds of evil things in hate of the Holy One Blessed Be He for they did not hate Israel because they served idols like them but because they would not do as they do. They served the Holy One Blessed Be He and keep His commandments and would not marry them and not eat of their offerings and insult their idolatrous worship and clear it out of their own places. As it says, "for You they killed us every day  (Devarim 33, 40)" . While the Ramban notes that the persecutors of the Jews 'hate' their G-d, he offers a naturalistic explanation for their hatred . Thus, at the heart of Jewish persecution is our religion. "Why is its name Sinai. Because from it there came forth hate (sin'ah) to the nations of the world (Shabbos 89a
Midrash Rabba in Pikudei (51, 4) goes beyond naturalistic explanations and describes anti-Jewish hatred as rebellion against G-d Himself.
R. Shimon Bar Yochai said: When Hadrian  entered the Holy of Holies he behaved arrogantly and derided G-d. R. Chiya Bar Abba said: David said before the Holy One Blessed Be He: So may it be considered before you that if they could cut down cedars and make ladders, they would have gone up to fight against you….except that they can't; therefore, they leave you alone and go against us. So it says, "They scheme, but they can't". …R. Chiya said: To what are the nations compared? To a man who hated the king and would have liked to overpower him but wasn't able. What did he do? He went to a king's statue and wished to make it fall, but he was afraid. What did he do? He took an iron nail and dug under its base (for ) he thought, "If I destroy the base, the statue will fall". So also the nations come to fight against the Holy One Blessed Be He but are not able and (so) they come against Israel ."
The same idea is found in the Psalms 69, 10 according to Rashi.
Because jelousy for Thy house hath eaten me up, and the reproaches of them that reproach Thee are fallen upon me.
This recognition that Ant-Semitism is a unique type of hatred unparalleled in the annals of human history greatly strengthens the thesis that it is nothing but a manifestation of Gentile resentment against Jewish morality  that has been foisted upon them in complete contradiction to their national character. This "slave morality' or 'morality of the weak', to use Nietsche's terms, with its restrictions and limitations on the use of power and joy of animalistic self-affirmation, sits uneasily on the broad shoulders of great hunter and warrior nations . It is this resentment that our midrashic passage so beautifully portrays as being at the root of Anti-Semitism.
See Meshech Chochma Leviticus 25, 18-19. A book length treatment by the Netsvi was published inEnglish as Why Antisemitism?: A Translation of "The Remnant of Israel " By Rabbi Naphtali Zvi Yehuda Berlin ,Translated and annotated by Howard S. Joseph
, Jason Aronson.
It is in this vein that the late Lubavitcher Rebbi wrote in 1954 that Holocaust is not a unique phenomenon, that it is due to a confluence of circumstances and that it could happen any time to any nation
Tehilim 44, 23. The verses 21-24 are probably Ramban's source.
R. Yechiel Y. Weinberg in a private letter to Samuel Atlas questioned whether Jews do not bear a share in anti-Semitic attitudes because of their attitude to the non-Jewish world, as quoted in M. Schapiro, Between yeshiva world and modern orthodoxy, Littman1999, p. 182. A similar explanation was offered by R. Israel Moshe Hazzan in Kerach shel Romi (1876). While some might be offended, put off, and summarily reject any such assignment of blame as erosion of health national pride under foreign onslaught, willingness to tolerate such speculation might also serve as evidence of deep humility and openness to self criticism that are a hallmark of pure religious personality.
Somje emend this to Titus to conform to other sources.
For the latest book length restatement see, Why the Jews? The Reason for Anti-Semitism, by Dennis Prager and Joseph Telushkin
Similar statements are found in R. Kook's writings.