This article has all sorts of excellent points, and this is certainly one of the best!
However, he says that Jews must come forward to combat Islam. Actually, Islam is a syncretist heresy (Jewish, Christian and pagan), so any one of them could probably attack it! But he doesn't address the issue of dhimmified Jews.
One of the reasons Jews were so unpopular in Spain at a certain point is that they sided with, funded and actively supported the Muslims.
Part of this was because the Germanic Arian (heretical) Visigothic invaders, who did not accept the Trinity, were anti-Semitic, whereas the Hispano-Roman Christians were not.
However, part of it was probably the fact that paying the tax was easier for them than for Christians, who were poorer and in the majority, and part of it was a misguided idea about how you could survive. Even Maimonides was briefly a Muslim, and in fact was denounced to the Inquistion by several French rabbis for his heretical beliefs.
I have always thought of these Jews as the secular Jewish pro-islamic leftists of their time, just going along to get along, and I think this is a problem that is with us today.
BTW, Jews had no state support at that time. There was no longer any kingdom, and even the Roman Empire had collapsed, so they probably figured the only way to survive was to make alliances. But their ally was not necessarily the best choice.