Because they were there.
Now, I have a bit of a beef with this column: he fails to acknowledge that the Evangelical Christian, today, is Israel's staunchest ally. I know, it's de rigeur to adduce the Crusades when assessing Jewish-Christian relations from a standpoint of "longstanding tension"; but, how many more centuries will be necessary in order to make some Jews and arabs cease to invoke that miserable episode?
I'm glad to say that some progress has been made, since this was (according to Allouette) written in 1988, as far as some Jews now understand that solid Christians back Israel.