The Psychology Behind Islam's Vendetta Against The Jews
Nonie Darwish, a Muslim brought up in Egypt who converted to Christianity, explains at Jihadwatch:

After a lot of thinking, analysis, research and writing I discovered that Jew hatred in Islam is an essential foundation to the Islamic belief system that Muslims cannot seem to be able to rid themselves of. Jew hatred masks an existential problem in Islam. Islam is terrified of the Jews and the number one enemy of Islam is the truth that must be constantly covered at any cost. It does not matter how many Muslim men women and children die in the process of saving Islam's reputation. The number one duty of Muslims is to protect the reputation of Islam and Mohammad. But why would a religion burden its followers like that? This is why:

When Mohammed embarked on his mission to spread Islam, his objective was to create a uniquely Arabian religion, one created by an Arab prophet, which reflected the Arabian values and culture. Yet to obtain legitimacy, he had to link it to the two previous Abrahamic religions, Judaism and Christianity. He expected the Jewish tribes who lived in Arabia to declare him their Messiah and thereby bring him more legitimacy with Arabs, especially with his own tribe in Mecca, the Quraish. Because his own tribe had rejected and ridiculed him, Mohammed needed the approval of the Jews, whom he called the people of the book. But the conversion of Jews to Islam was part of the scenario that Mohammed had to accomplish in order to prove to Meccans that they had made a mistake by rejecting him.

That was one of the reasons Mohammed chose to migrate to Medina, a town that had predominantly been settled by Jewish tribes and a few impoverished Arabs who lived around the Jews. The Jews allowed Mohammed to move in. At the beginning, the Koran of Mecca was full of appeals to the Jews, who were then described as "guidance and light" (5:44) and a "righteous" people (6:153-154), who "excelled the nations" (45:16). But when the Jews rejected the appeasement and refused to convert to Islam, Mohammed simply and literally flipped. The Quran changed from love to threats and then pure hatred, cursing and commandments to kill Jews. Rejection by the Jews became an intolerable obsession with Mohammed.

Not only did the Jews reject him, but also their prosperity made Mohammed extremely envious. The Jewish Arabian tribes earned their living from legitimate and successful business, but Mohammed earned his living and wealth through warfare, by attacking Arab tribes, some of whom were from his own tribe, and trade caravans and seizing their wealth and property. That did not look good for a man who claimed to be a prophet of God. The mere existence of the Jews made Mohammed look bad which led Mohammed to unspeakable slaughter, beheading of 600 to 900 Jewish men of one tribe, and taking their women and children as slaves. Mohammed had the first pick of the prettiest woman as his sex slave. All of this senseless slaughter of the Jews was elaborately documented in Islamic books on the life of Mohammed, not as something to be ashamed of, but as justified behavior against evil people.

One does not have to be a psychiatrist to see the obvious, that Mohammad was a tormented man after the massacre he orchestrated and forced his fighters to undertake, to empower and enrich himself and his religion. To reduce his torment, he needed everyone around him as well as future generations, to participate in the genocide against the Jews, the only people whom he could not control. An enormous number of verses in the Koran encouraged Mohammed's fighters to fight, kill and curse Muslim fighters who wanted to escape fighting and killing Jews. The Quran is full of promises of all kinds of pleasure in heaven to those who followed Mohammed's killing spree and curses and condemnation to those who chose to escape from fighting. Muslims were encouraged to feel no hesitation or guilt for the genocide because it was not they who did it, but "Allah's hand" was behind the killing.

Mohammed never got over his anger, humiliation, and rejection by "the people of the book" and went to his grave tormented and obsessed that some Jews are still alive. At his deathbed Mohammed entrusted Muslims to kill Jews wherever they found them, which made this a "holy commandment" that no Muslim can reject. Muslims who wrote Sharia, understood how Mohammed was extremely sensitive to criticism and that is why criticizing Mohammed became the highest crime in Islam that will never be forgiven even if the offender repents. Mohammed's message on his deathbed was not for his followers to strive for holiness, peace, goodness, and to treat their neighbors as themselves, but a commandment for Muslims to continue the killing and the genocide against the Jews.

Killing thus became a holy act of obedience to Mohammed and Allah himself. Mohammed portrayed himself as a victim of Jews and Muslims must avenge him till judgment day. With all Arab power, money and influence around the world today they still thrive at portraying themselves as victims. Sharia also codified into law the duty of every Muslim to defend Mohammed's honor and Islam with their blood and allowed the violation of many commandments if it is for the benefit of defending Islam and Mohammed. Thus Muslims are carrying a huge burden, a holy burden, to defend Mohammed with their blood and in doing so they are allowed to kill, lie, cheat, slander etc.