知識管理員, phc6amarcoho don't seem to understand the doctrine of collective responsibility.
As a committee member (chairman actually), he expressed, in public, views that are the complete opposite to what the committe expressed.
He could have talked about those when he was not the chairman of HKU student union. What he did is, he essentially gave out the wrong impression that his views are supported by the student union or HKU. As a former so- called HKU student (well... long story), I doubt that's the view of student union and HKU.
So in speaking out his view (which is against the committee's) he has violated the doctrine of collective responsibility and should definitely apologise (strictly speaking, he should resign).