I think the word "terrorist" is bandied about too readily these days, by the government, and by ordinary people. The danger is if it's applied too loosely, then at some point, everybody is a "terrorist," and the word loses all meaning. I think it's important to reclaim that word from government propagandists. A terrorist isn't somebody who breaks the law because they have no regard for the law, and it certainly isn't somebody who breaks the law in civil disobedience.
I think civil disobedience is an important response to social injustice where there is no possibility of redress through the political process. The civil rights movement is perhaps the best example we have in this country. I remember what happened when Bull Connor set the dogs loose on civil rights marchers-- white people across the country stood up and said "enough"! I saw it myself, even though I was young, because my parents took me to a march in support of the civil rights marchers.
Now consider what the outcome would have been had civil rights protesters surrounded a car load of children returning from a party and broken the windows out of the car. Would the country still have rallied in support of civil rights, and said no to segregation? I seriously doubt it. The marchers stood up to injustice; they boycotted the buses, they marched, they were nonviolent. They did not go out of their way to alienate anybody who wasn't a civil rights marcher. And when the police over-reacted with fire hoses and attack dogs, in defense of injustice, the country was shocked into action and the Jim Crow laws were finally defeated.
The traffic laws are in no way similar to the Jim Crow laws, and interfering with people trying to get home from work is not an act of civil disobedience. "It's a temper tantrum on wheels," to quote one Critical Mass defender. It harms cycling for the sake of gratifying the chip-on-their-shoulders temper tantrum. It's anti-cycling advocacy.