There's been a lot of comments flying around Facebook criticising the Council, but not as many condemning the Student's Union. I say neither side has the moral high ground. Prof. Li's attitude was certainly odious (but what else can we expect from him, after all he's done to Hong Kong?) and Prof. Lo did lie about being pushed. Politics meddling in university affairs is an issue to be addressed, no doubt.
However, the actions of the Student's Union was not justified at all. Instead of confronting the Council with reason, they hurled insults at them and barged into their meeting. These actions paint a horrible picture of the Union, indeed, the students supporting them. If the protesters were 'shoppers' in Mongkok, I can understand. Those people do not know better. Yet they are students of the most prestigious university in Hong Kong. They ought to know that barbarous acts such as these do not induce positive change; on the contrary, they only serve to undermine the very cause they are fighting for, by tainting the Union's reputation irreparably.
It's not like there is no recourse available. Perhaps they could have organised a school-wide referendum about the matter. That would have added much force to their arguments. Yet they did not do this. Barging into the meeting was a very bad move on their part, no matter how much negative PR the Council has since received.