Yeah, I think this is the key point that a lot of people miss. Step outside of our ideology for a moment and look at it from the perspective of a normalz. Would a red neck in a confederate flag shirt trying to arrest Obama for illegally making death panels or whatever convince you of anything other than that right wing nut jobs are idiots? A dude with an afro and a "beast mode" shirt trying to arrest Blair for an illegal war is essentially the liberal equivalent of a red neck in a confederate flag shirt babbling incoherently about death panels.
Sure, everyone who agrees already cheers, but everyone else is put off and thinks that this guy is an idiot. Not all, but a lot of protest methods I think are generally counter productive. I think the dividing line is "seriousness". If you look serious, people tend to take it more serious. If you look like you are having a good time or are an idiot, people assume that you are an idiot and your cause is more likely to be shit. Blocking whaling ships, cutting lines, and drawing attention is effective. Throwing stink bombs at those same ships is less effective because it goes from serious and life threatening to juvenile. People dressed in normal clothing holding a mass protest is effective. People dressed in costumes, waving anarchy flags, and having a concert are less effective because it either looks like a fun party or a collection if idiots. If I could be the dictator of any sort of march, regardless of the cause, the attire would be business suits, business casual, or (if you have nothing else) clothing you wear to your grand mother's house.
At least for me, what makes a lot of the old civil rights march video from the US look so gut wrenching and effect is that, even if you understood absolutely nothing about what the cause is for or its context, it looks like normal people being brutalized by police, rather than police chasing around belligerent and rioting kids.