Jews weren't hated when they fought back.
The hatred started when Roman emperors institutionalized Christianiy and began promoting the dogma of Jews, not the Roman authorities, being Christ killers. This marks the beginning of institutional antisemitism in the Roman world, from Spain to Asia Minor. By this time, Jews as a nation were not permitted to live in Judea, and were instead forced into slavery or diaspora, deprived of basic rights like property ownership and self-defense. They became easy and convenient targets, kind of similar to the old single women being accused of witchcraft later on.
With the rise of the Islamic Empire in the 7th and 8th centuries, Jewish diaspora in the conquered territories gained a special status under the Islamic law called "dhimmi". This status is written into law, and thus still exists as a legal benchmark in treatment of Jews in countries that adhere to Shariah law. By today's standards, this was a repressive regime of added taxation, legalized subservience to Muslims in all aspects of life, but it allowed Jews to practice their religion privately. By the standards of medieval Europe, however, it was considered rather tolerant and progressive.
In Europe, meantime, forced conversions of Jews to Christianity under the penalty of death became commonplace. Those who resisted but couldn't escape the persecutions were exterminated. In the more tolerant corners of Europe, Jews were forbidden to bear arms or defend themselves in any way, practice any trade or work the land. By default, Jews were pushed into money lending, retail sales and managing properties for rich landowners, forced into what we now call ghettos, wear insignia identifying them as Jews, and were only occasionally used as scapegoats to be accused of causing pestilence, or drought, or practicing witchcraft, or drinking blood of Christian children, etc., when indignant masses needed an occasional pogrom to quench their rage. This is when killing Jews just for being Jews was institutionalized under the rule of various despots, and as nationalism became prevalent in Europe, secularized and adopted by various "enlightened" secular demagogues in Europe . We can recognize many antisemitic tropes that were popularized back then being used today. This is how antisemitism we know today became prevalent in Europe, and this is how so many Jews became victims of wholesale extermination during WW2. For the most part, hey didn't fight back.
It was a huge surprise to everyone that, after WW2, and after the creation of Israel by the UN, Jews started fighting back for their country and their lives. Almost immediately, Jews not living down to the expectations the world got accustomed to in the course of the past centuries, this became the source of pretty universal outrage which transformed the nationalist antisemitism of the Nazi Germany into the internationalist antisemitism of today.
= new reply since forum marked as read