In reply to Labour democracy by Bruce
One correction to what I wrote above: what Harman did wasn't arbitrary. She had good reason to bar Woolas. But the powers the Labour leadership have do permit them to act in an arbitrary way: expelling members, deposing and imposing candidates without due process when it suits their political convenience.
On Matthew's point: Woolas was of course no less opportunistically racist when he was Immigration Minister in the last Labour government. Harman is denouncing him now because he has become a political embarrassment not because their politics on immigration have changed.