John Quiggin has two blog posts relating to this issue:
The Oregon Petition and looks for an equivalent from the left in the
follow-up.
Quiggin does make it clear that the asymmetry he sees is relatively recent, and I would agree. It's cultural, in the broad sense, rather than inherent.
Certainly there seems to be a case that currently the right is more in lock-step, holding to indefensible positions as a group than the left is.
(Found via
Deltoid)
Edited by PaulK, : Second URL vanished - was accessible via Deltoid link so no substantive change