No, but it makes Mubaraks emergency powers, powers created precisely because of Egypts widespread domestic terrorism, a lot MORE valid. Sure, their fears and frustrations are valid; what are the rioters doing to alleviate them? They're paving the way for a sectarian government guided by the principles of a man who listed individual liberty chief among his criticisms of the West; what does anyone expect that to improve?

Worse, there's strong reason to believe the rioters are aware of and accept that. Things haven't just "gotten out of hand". This isn't the Salt March or the March on Washington. It's multiple, deliberate, pitched battles with the military and police, with a lot of people have been caught in the crossfire. That Mubarak's an awful leader doesn't justify that, but that does suggest Egypt could and likely will do worse than Mubarak. Give me some reason to think otherwise and I might endorse his overthrow, but right now the BEST I can offer is no endorsement for anyone.

It doesn't seem repression, political prisons, torture and murder will end whatever happens to Mubarak, so I see no reason to pick sides.