Europe is basically a long history of wave after wave of immigration.

So is the US, and it's even more recent. Don't seek logic in it.

Yeah, mixing with those filthy homo sapiens was a bad idea...

I don't know much about the history of anti-Semitism in Europe (so anyone feel free to correct me or add more info), but what I've been thinking is that the cause/origin of anti-Semitism is no different from the anti-immigrant panic from today. They both come down to people from a "foreign" or at least different culture coming into a society and getting jobs or opening business. It just so happens that now those foreign people are more diverse, whereas before (centuries ago in Europe) they were mostly Jewish.

This tells me we have learned nothing from our past except for the most surface level details. We learned that anti-Semitism is bad and beat people over the head with it, but we never properly addressed the roots of it, and so now the same thing is repeating but for different groups of people. It's the same sort of thing as when it is said that "people nowadays are more open minded", when the reality is simply that they were taught to be okay (or not) with certain things; but the bigoted though process has not really gone away.