Jim,
No examples of genuine antisemitism have ever been produced.

Naz Shah.

Virtually all accusations have come from supporters of Israel

Errr, "The Labour Party supports Israel." (Deputy Leader)

or political opponents of Corbyn.

Almost the entire PLP are political opponents of Corbyn, so not surprising.

All accusations have been criticisms of Israel

Not true.

These attacks started within two months of Corbyn announcing support for B.D.S.

The problem only arose under Corbyn's leadership.