Long-term, honest public pressure can force an administration to make changes or change course on a failed policy. It works on domestic issues: witness the Porkbusters campaign, which has rapped the president and Congress without apologies in an effort to shame them into cutting spending.
The advantage of PorkBusters is that it's focused on one issue and been nonpartisan, criticizing porkers regardless of party. I don't think the kind of criticism Weigel's talking about can say the same, though I agree that it would have been more effective if it could. Anyway, it's nice to see that PorkBusters' progress is being noticed.