The union has *no* influence whatsoever on the Quartet boycott, and can do next to zilch about it. By contrast, there is a massive Palestinian campaign to obtain the boycott of Israeli academia and culture, and it is supported by Israeli academics. It has the support of sixty Palestinian unions and civil society organisations. The union was asked, like the NUJ was recently, to support the Palestinians in this, and it would have been ridiculous for the union to brush it aside or try and cover it up.
The hysterical response of the Zionists (like Dershowitz promising to 'ruin' anyone who supports a boycott) is indicative of how much support the boycott movement is getting in the UK and across Europe. And, after sixty years of doing next to nothing, I think it's important that people the British labour movement and the left is actually getting its arse in gear.