Mousavi and Khorrubi - for all their many faults - will get rid of the Besiji thought-police. And if Khorrubi got in, there would be legal protection for the private press and greater freedom for women.
A lesser evil really is more good than a greater evil. The Iranian people are crying out for the slightest relaxation of the grip of the Mullah state and the religious police.
And you would declare their vote an act of intrinsic evil? Shame on you.
And that's why we see so many pics and youtube videos (aside: good pics here) of Basiji beating up pro-Mousavi demonstrators. What we may be seeing is a factional split within the ruling mullahcracy, with some getting uncomfortable with the power of the Revolutionary Guard and the Basiji.
Who says so that has any power?