Of course there are times when violence is justified. You cannot just give in to authority, there are times when you have to stand back up and demand for your right. If your demand remains unanswered you have the right to fight for your right. I will list a few instances where I believe violence is clearly justified.
If your labor does not earn you roti, kapra and makan you have to work harder, if you work harder (as hard as someone else who gets roti, kapra and makan) you have the right to protest. If your protest is unanswered you have the right to be violent.
If your basic human rights are being violated, you can protest. Again if your protest in unheard you are justified in being violent.
Also, the worst form of oppression deserves the worst form of rebellion.If you can’t afford the increasing petrol price you can come out on streets with placards and that is not violence because this situation does not ask for violence. If your right to life is being violated you have the right to protest more violently against the oppressor. Make sure your violent protest is against the oppressor not the innocent.
Rebels usually forget to distinguish the oppressor when they come out on streets to protest. Their violent protests harm (physically and mentally) innocent people more than it harms the oppressor. The important thing is to target the oppressor. If it is not possible to harm the oppressor physically find another way to do it. Form a union, bring people together for the cause and then target him. If, however, your violent protest harms innocent people you become an oppressor too and your case or your right to violence grows weaker.
Violence comes in degrees, we have established that and so you must rebel justly. For instance, if X kills your brother and you rebel by killing X’s brother, you have dismissed your case and your right to rebel is over. If you intend to kill more of X’s family members because he killed your brother, you are going to become the oppressor now and not him. So there is a point till which violence is justified, beyond that point you might not be the oppressed and so you do not retain the right to rebel.
Violence is your last weapon which means you should pick it up only when there is nothing else you can do about it. There are non-violent protests that have proved successful which is why it is important that violence is avoided till there is no alternative. Also, violence should be targeted. Don’t just go killing everybody, that particular kind of violence cannot be justified in any way. In the name of religion or in any other name, you have no right to other people’s lives. Which means if your violence is not targeted and it gets out of hand, you become the oppressor. It should be the last option to make sure that your case remains strong and you don’t end up being the oppressor.