If the DDOS is being launched from the protester's own machine, I'm OK with that. The protester or protesters should, of course, be prepared for the consequences of their actions, such as being arrested and/or sued.
However, if the DDOS is being launched through a botnet, on machines that have been compromised, then I'm not OK with this being a form of protest. There is no accountability, and the participants in the protest are not willing. It's (very) roughly equivalent to drugging and brainwashing thousands of people and then turning them loose on the streets.
In general, though, I think that anyone who uses DDOS attacks should be subjected to a year of defending against them.