I find it depressing that Juan Williams was fired from NPR for musing about his fear of Muslims on a plane, for the same reasons Conor Freidersdorf lays out: Being afraid of Muslims on a plane is ridiculous, because the percentage of Muslims who are terrorists is minuscule, but the bar for firing people for a single remark ought to be quite a bit higher than this.
Matthew Ygelsias applauds the firing because Williams is a mediocre, "replacement-level" commentator. That strikes me as a total dodge. Most commentators -- most members of every profession! -- are average. The question here is whether we want to create an atmosphere where commentators need to live in fear that even contemporaneous comments will be scrutinized by the strictest standards of tolerance, and a one-strike-and-you're-out policy is generally applied toward their employment.
I also opposed the firing of Helen Thomas, and Lord knows the hacks don't get much hackier than her. There's a value in stigmatizing bigotry, and there's also a value in allowing political commentators some level of freedom to opine without fearing their job is on the line at every moment. The way to steer between these two poles is to combat misguided or bigoted speech with criticism and stigma rather than firing, except in extreme cases.