I already told you I'm not going to tell you explicitly where the line is in my personal opinion. I don't sit back and go "murder is too far, but robbery is alright" because that's not the point. It's based on the circumstances of the situation.
I feel like this situation (violent protestors lashing out against civilians) parallels perfectly with the situation in Benito Cereno, where the slaves become free and not only kill (or attempt to kill) their direct oppressors, but also the civilians who were merely allowing the oppression to exist and continue. When I analyzed this situation, I felt as though the oppressed were justified in killing their oppressors and the people who were indifferent to their oppression. Murder is not ethically right. I do not condone murder. However, I understand the sheer rage that the oppressed feel, as a result of the evils committed by their oppressors, and therefore see their acts of revenge as justified in a sense. I hate to witness these acts of revenge, but I understand their existence, and understand that they are justified.
In relation to this specific situation, I do believe violence is justified. I hate to see it happen. I wish that it wouldn't happen. However, I understand why it happens and understand that it is a terrible byproduct of intense oppression. Millions of lives have been ruined and destroyed by the oppressors, and the people who remain indifferent are doing nothing to help their fellow human beings. Humans are dying, yet nothing is done. This creates intense rage from the oppressed. Rage that is channeled into violent acts. Violent acts that, as a result, are justified.
In conclusion, there is no simple answer. Everyone will perceive this situation differently. I am someone who empathizes so greatly with the oppressed, that I have been criticized before, just as I am now, for going "too far" in believing that their violence is justified. It actually pains me to say this, because I know that it seems like I am advocating for violence, but I'm not, and I hope I am not portraying that with these statements.