Clarification 1: the boycott of Israel
A boycott is indeed a difficult thing to pull off. Economic boycotts - not buying Israeli products - or divestment campaigns - don't invest in Israeli firms - are complex enough. But cultural boycotts, academic boycotts, humanitarian boycotts (effectively what the anti-Zionist doctors are proposing) and news embargoes (effectively what the NUJ anti-Zionists are proposing) are even more complicated, and arguably are extremely counter-productive in that they target the places where hopes for peace are located.
I do not think that the Israeli state has an admirable human rights record, and if my union had a consistent international policy that said we will boycott all states that commit a certain set of clearly defined humanitarian abuses, and Israel happened to be one of them, then I’d probably support the boycott.
But Israel has been singled out wrongly here. Look at any one of its crimes, and they have been committed by other states too. Including, as Nick points out, the US, not to mention the UK. And when one state in the world is singled out as the source of all evil, you have to ask why.