My own pacifism stems from my very nature. Even though I studied to Purple Belt in Ju-Jitsu, I was incredibly bad at sparring with actual opponents. Any attempt to hit a person, I somewhat pulled back from, focussing instead on defence.
That said, I'm not actually a great believer in pacifism as protest. It's great as long as everyone involved is a pacifist, or on a small scale. Many times in my school days, the everyday casual bullying that sometimes escalated to the point of actual physical violence, I managed to avoid very simply by not playing that game. Instead of getting angry, I simply deflected it with a casual dismissal. I have learned that it is surprisingly effective in a casual face-to-face encounter. Of course, had there been any true threat of violence, I'd have been fucked.
Sometimes people would throw little stones at us, and miss repeatedly. So we'd keep walking, or perhaps do a little turn and pull out a corny thumbs up, or the slow hand clap. They threw more stones. But man, those times were worth it.
Anyway, I genuinely believe that at a certain point, even in our day to day lives, violence is the answer. Sometimes people need to be punched in the face. See The Flaming Lips for a more articulate expression of this:
When it comes to a large scale, pacifism is kind of ridiculous - and yet, often it is the only option. Not to trawl up that horribly misappropriated "first they came for the..." line or anything, but I'm going to flip it around on you. Notice how in that line, they never came for the guys camping out in the hills with the guns? The kids at Tiananmen Square who died, basically died for almost nothing, and now China's too big for anyone to control. Sure, now we all know about China's appalling human rights violations, but kids in their own country can't even read about that. And all over wanting to eulogise one guy. Kind of a crappy thing to be killed over, but that's what you're dealing with when you can't back yourself up with equal force.
So basically, pacifism is groovy and all, but you can't put flowers into guns and not expect to be shot.