It's actually not hard to argue that defined benefit plans should be done away with; the second clause in the excerpted statement tacitly makes the argument. As politicians are irresponsible as evidenced by chronic underfunding of pension funds (and improving benefits in the future that they have no intention of funding) a better retirement policy would be to shift towards defined contribution plans where politicians cannot kick the can down the road. Not difficult. I think Ezra puts in a lot of good reasons why defined benefit plans are good, but the political economy considerations remain the same. If the media were more vigilant about accurately reporting on deficits (you have not posted a surplus of $x if you have skipped a pension payment of $x or $x+1) then I would probably be more amenable to defined benefit pensions because when they are run properly and when they are funded adequately they are a superior solution. But I think the incentive will always be for politicians to promise more benefits in the out years and skip funding in the present creating problems for future taxpayers and retirees alike.
Update: Andrew Samwick and Megan McArdle have great posts on defined benefit plans and retirement savings more generally. One of the the things both discuss in their posts is how people get screwed when they switch employers in a defined benefit context. I think this is an underappreciated aspect of pensions. Once upon a time it was more likely for folks to stay with a single employer for their whole career, that is less and less the case.