I don't know about this case, so I can only speak in general.

A lot of times people that say this don't make a strong case that some theoretical more moderate protest would be effective. There is just a feeling that if they personally feel offended by the actions of the protester then it's probably a bad thing.

In reality it's often more complicated. I know some people that are involved with controversial protests, and the effectiveness of their actions is definitely something they think about. It can't be too extreme, that will put people off like you say. But often there is conversations like in this thread, "this protester goes too far, but they do have a point". This moves the Overton window in the desired direction.

The goal isn't too make you like the protester, it's to make you think about the issues.

Worked for the IRA. Working for Hamas. Working for the Islamic Republic.

Cowards would have you believe otherwise, but force is sometimes the only way to get what you want.

It really doesn't matter if you come across as the villain as long as you impose great enough costs for not delivering your desired reality.