The protesters accused Campus Watch staff of a "gross overreaction" to a "peaceful direct action", in which they planned to occupy the clocktower.
One person was detained by a Campus Watch staff member, and after an altercation a glass plane was smashed.
Mr Robertson, the university's vice-chancellor, said yesterday the protest "crossed a line".
The School of Arts has now postponed a lecture which Mr Robertson was scheduled to deliver in the Burns lecture theatre at 5.30pm.
"This event has been postponed due to security considerations," the university said on its website.
Mr Robertson's activism in his student days included marching on the clocktower.
Organised by Otago Students for Justice in Palestine, yesterday's rally was calling on the University of Otago to suspend collaborations with Israeli universities and join the BDS (boycott, divestment and sanctions) movement against Israel.
A spokesperson for the group said the protest was planned as "peaceful direct action", in which they planned to "occupy" the clocktower.
"We were obstructed by Campus Watch, who physically blocked us from entering the building."
The university has been approached for comment.
