The optics (at the moment) seem to be the most important issue here. Whether or not the vote is legitimate is quite irrelevant in immediate aftermath. This is a government using physical force against its citizens for, of all things, voting -- a core democratic principle.

Democracy must be tolerant of peaceful protesting. An "illegal" vote (depending who's lens we are viewing this from), to me, is a form of peaceful protest. Candor, mutual respect, and peaceful organizing are some of a few tools democracies have to solve problems without devolving to unrest and violence. If we assume we highly value avoiding violence (and we should), governments need to tolerate the use of these tools, from time to time.

By banning the use of these more moderate options, the national government is essentially promoting dissenters to even less desirable options so they have at least some form of expression. I think we should be surprised the national government chose to use such force when it had far less invasive means for dealing with the consequences of this vote, e.g., courts.