I wouldn’t mind that the AUT was generally crap at politics, or that there hadn’t been much internal union deliberation if the policy adopted by Council clearly reflected the will of the majority of AUT members. But there’s no reason to think that it does. I don’t think the boycott motions would survive the test of campus ballots, for example. Nor is this just a matter of members versus their representatives in Council: there are divisions among the activists themselves, for the boycott motions seem to have been passed by Council fairly narrowly.
To conclude this bit of the discussion: unions that are crap at politics, and without an especially good record of widespread internal deliberation among grassroots members, should, on the whole, refrain from adopting obviously divisive political motions.