"unless those movement leaders were behaving violently"
What you consider violent and what the police consider violent isn't necessarily the same thing. "The individuals who linked arms and actively resisted, that in itself is an act of violence" [0]. Read comments on YouTube [1] for extra confidence in humanity. In reality you don't have to be violent to get beaten and arrested by the police, you essentially only have to not comply with whatever they say.
A little poke from a baton will do more to harden a protester's stance than scare them off. And it will create massive backlash by spectators.
The fact that you're pulling out a 4 year old article about it shows how counter-productive those tactics are.
Even though I don't have any opinion on that particular protest (I don't know what it was about), I think that whoever let that happen should be sacked, because it would have only escalated the protests.
What you consider violent and what the police consider violent isn't necessarily the same thing. "The individuals who linked arms and actively resisted, that in itself is an act of violence" [0]. Read comments on YouTube [1] for extra confidence in humanity. In reality you don't have to be violent to get beaten and arrested by the police, you essentially only have to not comply with whatever they say.
[0] http://www.sfgate.com/news/article/UC-cops-use-of-batons-on-... [1] https://www.youtube.com/watch?v=B_f06VQOkI4