>What are the Jews doing so wrong?
They were key players in moneylending (which both Jews and Christians agreed was exploitation, but as long as Jews were willing to do it to Christians, it was regarded as acceptable). Much money was made via tax-farming which also rankled the poor peasants who had to scrounge up that wealth. "In the [Muslim] surrender treaty of 1492, the last Muslim king of Granada inserted a clause stipulating that no Jews would be allowed to have authority over Muslims or collect any taxes from them." Jews were frequent choices to be estate-managers (they were far more literate, after all), and therefore were stuck with the position of evicting nonperforming peasants from their farms, and so forth. (It was also better to hire a Jew to manage an estate than a Christian who might be coerced by family pressures to give his relatives an extension, and then make up for that shortfall by squeezing non-relatives even harder.) They were also major players in the slave trade of Europeans. The historian Ariel Toaff has said that gentile fears that led to the infamous blood libel incidents were more likely an offshoot of fears related to Jewish-connected slave traders abducting Europeans. Some other activities were also regarded as exploitative -- e.g. in tsarist Russia, Jews were heavily involved in the liquor industries.
The line one often hears is that Jews did this because they had no other choice, but recent Jewish scholarship tends to the opinion that they actually sought out these wealthier jobs (and those that stayed as farmers and as more menial laborers were less likely to remain Jewish, since they couldn't afford the costs of making their sons literate, so there's a "survival of the richest" effect in evidence, though later on, once a flood of poor Jews entered the Pale, it would be easier to be poor and remain Jewish.)
EDIT: It's true that most Jews -- the vast majority -- did NOT engage in these activities (except for liquor, which was indeed the main source of employment for Jews in Russia until the tsar put a stop to it, and of course, for every person who considered the liquor industry to be exploitative, there were others who just wanted more of it). But the fact that most Jews weren't moneylenders or tax collectors is beside the point. If someone were to me an analogous question of what was it that whites were doing to blacks that was so bad, it would be dishonest to omit things like slavery and lynching, even though there, too, only a small percentage of whites owned black slaves or lynched black people. The same is true here. The activities I mentioned loomed very large in the gentile imagination, and helped drive a lot of the resentment (and antisemitism) that, as we all know, frequently led to murderous violence. The Jews aren't the only people known for nursing resentments and harboring grudges. I'm not justifying any of those resentments, but I'm not going to lie about what caused them. I also get tired when people try and reduce issues like Northern Ireland to being simply a case of religious intolerance. It is much more than that, and mostly involves politics and economics. The same is true of the resentments Jews and gentiles felt towards each other.
>The people were exploited by their rulers and by the Church, not by the Jews.
But they tended to hire the Jews to carry out the exploitation and that's important. We don't absolve a hit-man from murder just because someone else ordered the hit. The Jewish kapos who lorded over fellow Jews in the Nazi camps don't get a pass just because the people running the show were the Nazis. In fact, I get the impression that some of the Jewish survivors hated the kapos as much or worse than some of the Nazis. And the kapos really didn't have much choice. The Jews, according to recent scholarship tended to seek out the money-lending and tax-farming jobs for the advantages they conferred.
>Money lending was one of the few businesses the Jews were allowed to do.
Cry me a river. The serfs and peasants were basically PROPERTY of the manor. How much job-mobility do you think they had? And they where the MAJORITY of Europe's population for a long, long time. I'm sure their ghosts are crying in agony because ship-owners didn't want Jews who had gotten wealthy from moneylending and tax-farming to muscle in on their guild and their turf.
Again, take it up with the Jewish Encyclopedia, the World Zionist organization, the history dept. of Hebrew University, and the authors of the book The Chosen Few one of whom, I believe, is an Israeli economist with the world bank. Those were my ultimate sources (a few of which I found via Wikipedia).
If even that is anti-Semitic in your head, that says more about you than it does about me.