Of course the sending of tanks is a threat of violence, but the threat was enough that most walked away. There were discussions with protest leaders and necessary changes were all considered. The ones which the party determined to be valid were taken and others rejected. It was a largely liberal and student-oriented protest, though, with many feelings which were opposed to working class interests, and those were dismissed. Then, after weeks, one of the busiest areas in the world had to be cleared for the resuming of life there as it was for the people living there. This is already fine, to me, because the debates occurred and the interests/benefits were considered in a democratic way. Also, note, this ignores that many unarmed army were murdered and therefore the threat of force had to be much more direct (not just an soldier who will be defended by more/new ones with guns, but actually just sending the guns so those soldiers could defend against their own lynching)