...this bill didn't have the potential to kill MORE people than it saved, or ruin more lives. 

We are assuming that the government subsidies for the uninsured will always be there, helping people afford the extravagant hikes in premiums.  We as a country may be essentially out of money soon (for a variety of reasons).  Those subsidies will very possibly either be cut or run out of money.  What happens then?  More uninsured people than now (because no one can afford the coverage, and the government can no longer subsidize aid toward such), and all future efforts at "reform" will be squashed by popular opinion via the false argument that "this government takeover of Health Care just bankrupted us further--we have to let the private industry completely annex the terrain again."

Mandates with no cost controls simply allow the insurance companies to both take (by force) our money directly and through our taxes, while not covering many more people than they do now.  When the government subsidy money runs out (or the bill is rendered totally worthless other than the mandate), it doesn't matter if they can't deny pre-ex-cond patients--no one will be able to afford the coverage.  And this doesn't even take into account how many lives will be ruined by the new abortion ramifications.

On top of this, while your argument is about the policy, and I predict a different outcome than you do when the policy is implemented, the politics of "needing to pass _something_ just so we can make it better in the future" is disastrous.  The Democrats will look back at 2009-10 and they are not going to want to touch this issue until at least 2017 or 2021 when maybe a new Democratic president takes over and our problem is more dire.  The days when Democrats charged courageously forward in their long battles for the under-privileged are over (unless there is a dramatic change), so thinking about the successes of bills that passed in the 30's and then slowly were tweaked in the 50's and finally became real Progressive victories in 1965 or 1973 have nothing to do with today's political climate.  That might as well been 1765 and 1773.

So the Democrats are not IMO going to try to make this bill better, and the media will blame the Democrats for the bill's failures for the rest of time, and the voters will take out their anger on Liberalism, the influence of which is COMPLETELY foreign to this bill.  Even if most of the Democrats were not corporate shills who emphatically preferred Health Industry bribes to courting votes from their base, if they are so weak in their negotiating position that passing a truly horrible, unpopular bill is a "positive victory" for them, they will continue to get walked all over by everyone.  You have to have a point beyond which you just have to walk away.  What is that point with this bill?  How will the Democrats ever be taken seriously if they do nothing but concede point after point, get no compromise for their concessions, get full blame, get full incendiary rhetoric, and wind up with an expensive, intrusive, nonsensical piece of garbage as the ONLY thing they can produce as their legacy for the future?

How is any of this irrational?  When you have something that isn't popular, largely isn't helpful (and makes problems worse, for the most part), throws away all of your political capital and credibility for years to come, and perfectly epitomizes your weakness and failure and pathetic squander of monumental opportunity, the most rational thing in the world is to get rid of it and cut your losses.  And if/when the Republicans win for the next 3 cycles because you threw this albatross away, so be it--blame yourself for not ramming through a robust Public Option in a robust bill via reconciliation last September.  At least your name is not (as) besmirched by it for the next 15 cycles.