I agree with Kevin Drum that this kind of nonsense needs to be fought back every single time.
This nonsense needs to be fought at every turn. Democrats have to make it absolutely clear, every single time somebody spouts this rubbish, that supporting the Iraq war doesn't mean you're "on offense against terrorism." Nor does opposing the war also mean you oppose fighting jihadism. The truth is closer to the exact opposite, and chapter and verse should follow if necessary.
This needs to happen Every. Single. Time. We can't allow the Rudy Giulianis and Dick Cheneys of the world to get away with this. They've dug us into too deep a hole already, and we can't afford to let them dig it any deeper.
But one of our biggest problems when it comes to messaging is that Democratic leaders are not disciplined enough to consistently hit on a point until it starts to stick. So, even if a few Democrats here and there hit back with the "Iraq != War On Terror", they don't do it enough to make an impression.
Worse, several Democrats contradict this message and they generally tend to get a lot more media attention.
One thing I always appreciated about Howard Dean (and still do) was his consistency. He would repeat a point over and over and over and over again. So much so that I used to joke with fellow supporters that we could recite his stump speech chapter and verse by the end of the campaign. People who follow politics closely may find this tedious because they have heard it before. But it is this kind of repetition that eventually begins to change the dialog.
Say what you will about Republicans, at least they understand the importance of consistent messaging.