If those are the issues you're concerned about then I don't think a Pirate Party is actually helpful.

But it's an interesting question: if you want a certain type of political change are you better off forming a crazy extremist group or a modest mainstream one?

I think the extremists are more effective. While people don't take them as seriously, they do move the balance of the discussion. It's like a see-saw {balance}. Where do you put a limited weight to have the maximum effect. Groups like The Sierra Club were ignored or seen as pretty fringe, until groups like Earth First came onto the scene.