The reason why the German Greens are so crap in power is the same reason everyone is crap when they're in power - the proximity to power turns people authoritarian. Jack Straw said so much col stuff in opposition - much of it not big vote-winners - yet when he became home secretary he became the bastard son of Michael Howard. Ditto Blunkett.
Grufty Jim said he saw a half-hour interview with William Hague (who??) the other week, and he's turned into a humane and honest person. He openly admitted mistakes (listing his biggest as 'not stopping Jeffrey Archer sooner'). But when in power all issues pale beside the need to STAY IN POWER. And so they're always vicious, point-scoring and trying to seem in control and invincible cos they love their power so, irrespective of how they use it.
Centralised and parliamentary politics are the only true single-issue politics, the single issue being the acquisitiion of power.
This is why any change of government, or even any revolution leading to a new centralised power structure, makes only superficial changes and can only give us authoritarianism and misery.
This is why i'm just as against the elite vanguard socialists as much as the capitalists and fascists.