What's the most futile form of protest?

I would disagree. Yes only peacefull protests don't get you what you want. Similarly only violent protests don't get you what you want either.

MLK needed black panthers and Gandhi needed Subhash Chandra Bose.

The violent protest gives the people temporarily what is needed much more than freedom. A safe space to express themselves peacefully. And that is what eventually leads to freedom.

So for any resistance you need both peaceful protestors with a uniting figure and a violent protester to create a free space to let the peaceful one grow.

It's a non-violent protest that demonstrates one's willingness to die for the cause. It hasn't worked recently, so I suggest anyone considering it put their life to better use.