This could've been done much more effectively. The University has the right to remain apolitical, where or not this goes against morality irrelevant. The uni itself is about education, on the other hand the Union is a political institution - represents the interests of students naturally.
So really, these guys could've occupied the gallery, and they would have a lot more banner space. Also, they could've hung a banner on the bridge above the concourse, and even going further by setting up tents under the bridge (effective 'occupying' the concourse). If they had done this, then I would've supported the occupation.