Deterrence? What's That?

So, I'm scarcely a fan of throwing reporters in jail for protecting confidential sources, but this New York Times editorial makes an incredibly silly argument:

If she is not willing to testify after 41 days, then she is not willing to testify. It's time for the judge and the prosecutor to let Ms. Miller go.

Which is in the same league as claiming that there's no point jailing a murderer if you're sure they won't do it again. As David Friedman pointed out in his great law and econ primer Law's Order, this misses a good part of the point of punishment: It's not just about the person imprisioned, it's about creating incentives for others not to engage in similar conduct. By all means, let Miller go, but not on the basis of ass-backwards arguments like this one.