When it comes to political violence of today, it is not a very prominent thing in the United States. It does become very visible in other countries, and it is something that very rarely is ethically justified.
When I began to think about this topic, my first reaction was no, it is never justified, because your government is what is in charge, and unless you live in a democracy, you basically have no say so in what goes on. After thinking about things that have happened over time, and things that have happened recently in the world, you could assume that it is at times justified to have political violence against your government.
A perfect example of when it is justified would be in the era of Hitler's reign over Germany. This is so because Hitler was doing things that were immoral in itself. The life quality in Germany was horrible, especially if you were something or someone like a Jew.
If someone were to have brought violence to him to overthrow him, it would have been completely justifiable. Often though you do not find those kinds of people who are going to do that in your own country, in this case, it was not until other countries stepped in and waged war against Germany that the government in which Hitler ran was overthrown. So, in the since of violence against the government, this is a perfect example of when it is justified, and necessary to have, in order to have a greater quality of life, and a successful life of your nation and government.
Many people would say that it is still not justified, because Hitler is still in charge, and he is still the commander of the government. No matter if what he is doing is wrong...