Richard,
What some have appeared to argue is that if not enough is done about Isis it somehow justifies Israel's (actual or alleged) war crimes. That is another manifest stupidity.

No.
It is the massive emphasis only on attacking Israel for its actions.
Guardian 3 days ago,

"Why the disproportionate coverage of Israel? "Jews are news" many say, with a shrug. But this obsession with Israel's conduct tacitly encourages the easy slide into hostility towards Jews.

First, the reporting gives the false impression that the situation in Gaza, though tragic, is uniquely horrific. Compare it to the silence surrounding Isis's frightening rampage through Iraq: Mosul has been emptied of its ancient Christian community; hundreds of thousands of Yezidis have been cleansed from Nineveh province. Compare it also to coverage of the plight of Palestinians in Syria, where thousands of Palestinians have been killed and the Yarmouk refugee camp remains under siege. How many newspaper front pages have been devoted to these events?"

http://www.theguardian.com/commentisfree/2014/aug/07/gaza-coverage-rise-antisemitic-attacks-europe