There is are a few exceptions to the rule:
- When one's nonviolent civil disobedience will be met with official intentionally lethal force - we're not talking about a couple of policemen beating a man to death, or a man with a heart condition getting killed by a taser, but an official policy of utilizing lethal force against protest - violent protest is completely moral in that circumstance.
- When nonviolent civil disobedience will not achieve the stated goal, and there is no chance of changing official policy through peaceful means it may be necessary and moral to engage in violent revolution. This is highly situational and depends entirely upon what is being done, and the possibility of peaceful change, rather than the system of governance.
- When nonviolent civil disobedience will be met with excessive penalties (but not violence), one must make a decision - will they continue to fight the good fight in the land of their birth, accepting the previously noted excessive penalties, or will they leave for greener pastures?
If you want to protest speed limits by having a convoy speed past a police station, it does no good to lead them on a high speed chase to avoid having to pay the inevitable ticket(s), but instead have the entire convoy pull over and pay their individual tickets.
Eric Snowden doesn't qualify for sympathy. He didn't accept the consequences of his actions, and in addition to leaking information about the NSA spying upon US Citizens, he also leaked information about the NSA spying upon foreign governments. No matter what happens, he is legally liable for all of the leaked information, including information which will be used by foreign governments to give them an advantage over the US.