. . . I've read a good deal about Handel in general and the Messiah in particular. The connection to Zadok is obvious to anybody who listens, the whole idea that it's anti-semitic is nonsense.
The English really did think of themselves as the new "chosen people" . . . I mean, think of the British-Israelites. This is more or less the period (he was about 20 years younger) when you had Sam Johnson roaring in big caps that he was a "TRUE BORN ENGLISHMAN!" . . . and that was the context that the English considered the Old Testament in. I don't think anti-semitism was really on their radar, other than the usual casual and dismissive attitude the English have always had to the non-English of any stripe. Certainly not important enough to make it the focus of an entire oratorio!
. . . wonder why the writer didn't zoom in on the fact that Handel was actually . . . oh the horror! . . . German.
Barbara Tuchman wrote that for the English Puritans their true ancestors were the ancient Hebrews,not the inconveniently papist Anglo-Saxons. Cromwell let the Jew back into England about three hundred years after they had been banished. Yes, the English were and are xenophobic, but usually in a nice way. Disraeli was, after all, allowed to be prime minister, even though he was very exotic.