In an excellent analysis  of the disastrous effects of Obama’s latest betrayal, Krugman startled me twice.

The first strange note is

I’ve spent the past couple of days trying to make my peace with the Obama-McConnell tax-cut deal. President Obama did, after all, extract more concessions than most of us expected.

Maybe it is an rhetorical device (such as “Brutus is an honorable man”) –  but I found myself wondering: Is it Krugman’s job to try to make peace with whatever Obama does? Should he even write that? Well, apparently so.

To be sure, he doesn’t make the peace and goes on to correctly explain why the “hostage release” Obama negotiated secures the captors with new hostages – including the risks to Social Security and Medicare .

But before daring to speak up, he  becomes defensive by stating

Yet I remain deeply uneasy — not because I’m one of those “purists” Mr. Obama denounced on Tuesday but because this isn’t the end of the story.

And do prove it, he spends a great deal of his column analyzing  the bad political effects of the deal. Mostly on Obama (economy will worsen right before the next election).

Maybe the argument needed to be made (not only you damned millions to poverty but you harmed yourself), but not from a defensive position.

By doing so, Krugman appears to be telling Obama: please, don’t insult me, I am looking out for your best interest here”

So, when he correctly  concludes that

The point is that by seeming angrier at worried supporters than he is at the hostage-takers, Mr. Obama is already signaling weakness, giving Republicans every reason to believe that they can extract another ransom.

Krugman can apply this argument to himself too: by appearing more concerned with the adverse impact of the deal on Obama than on the people, Krugman is undermining his credibility. Or, signaling weakness.

Because by declaring that he is not a purist, Krugman begs the question: who are the purists and when can we round them up?

Because by exempting himself from Obama’s attack, Krugman also legitimizes it – and that’s the last thing we need from him.