Tanith - no-one is disputing that there are Jews in the Labour party - the issue is that Corbyn seems to have difficulty with them. hence Chakrabati Report, widely seen in the Jewish community and elsewhere as a whitewash.
Also, his appearances on Iranian television, his fondness for radical Islamist groups, Sinn Fein, Chavez, his invitation for tea in the Commons to someone who accused Jews of baking gentile children into their bread.
Unsurprising that support for JC in the Jewish community is well below 10% (yes, I know most of those 10% will be on MN....)