So let's make a few important points:

(1) There is antisemitism in the Labour Party
)2) It ought not to be there, and has been allowed to creep in through laziness and political opportunism.
(3) It is no more prevalent than in society in general - it ought to be much less prevalent because members should be more aware.
(4) It is not confined to Corbyn supporters
(5) Criticism of Israel is not necessarily antisemitic (it can be), and no community can be immune from criticism.
(6) Many Jews are not zionist - now and historically. They are not antisemitic either.
(7) To claim special status for any so- called racial group- whether negatively or positively- is racism
(8) If you justify any form of racism, you implicitly justify all - including against youself. Racism is indivisible.
(9) Remember that there is a powerful force operating in politics- spin. This "antisemitism" episode bears all the marks of a political ambush, in its timing and biased application. It's a bad idea to tie important principles to ephemeral events.

I would have thought it unnecessary to emphasise these points, but some people seem determined to try to make the issue simplistic. You will also note that the term "racism" is too restrictive, and we really need a different word to cover the whole complex of religion, ethnic history, DNA heritage, and cultural tradition. For example, Muslim Bosniacs are genetically indistinguishable from Christian Serbs. The only difference is their ancestors' cultural response to the 15th centuray OIttoman invasion.