Protest and purpose

I've ambivalent about protest marches. I get that people want to express their outrage, and the marches can bring needed attention to issues. In the case of Trayvon Martin, I'm pissed, too.

What, though, was the point of a Martin protester blocking a light-rail vehicle in San Jose today?

What did the people on that LRV have to do with Martin's murder?

What did the transit authority operating the LRV have to do with Martin's murder?

Another thing: even on a Sunday, people have to work. People have obligations other than work, too. Protesters who deliberately screw with traffic, then, aren't just "inconveniencing" people, as their apologists like to claim. They are adding stress and difficulty to the lives of people who not only did no harm to Martin, but have no power to redress the injustice of his death.

Why piss them off about your protest rather than whatever you're protesting?