Well just speaking for myself, he has lost my vote due to his stance on this, and the vote of a few others in my circle who are labour leaning. Which is a shame because despite being a bit boring, I've often championed him against a lot of people I know who say he doesn't offer anything. A man who says the things he's said on this clearly is no principled man and will just do whatever the people behind the scenes tell him to do.
The problem is of course who else to vote for. The Lib Dems are no better - Ed Davey had the exact same stance of 'Israel has a right to defend itself' that's been pushed out to pretty much most UK politicians. I haven't checked out the Greens, but the first past the post system gives them no hope of doing anything. So possibly just leads to another abstain, from me.