The difference between this and computer security is that when a security hole in software is announced, crackers may exploit it for a while before it's plugged, but that's okay, because the point is that it's eventually plugged and that's good for the long run.
In the case of terrorism, you can't afford that time lag between discovering the hole and plugging it, because terrorists may use that time to perform an attack, and such an attack as a much more significant impact than knocking down a few servers.
Does this mean that it'll take longer for us to secure our country? Yes. Does it mean that, since terrorists are also not as smart as the whole world, we will prevent some acts of terrorism because the terrorists didn't think of them? Also yes.
Did the terrorists read Debt of Honor or think up the idea themselves? Let's assume they did. So we have two choices here:
(1) Open up all possible terrorist strategies (which will happen to some degree anyway, given our free speech, though this is an aspect of free speech that could potentially get limited in the interests of "national security".. but that's not something I want to get into right now). Result: When a terrorist strategy is announced, there will be a race between the gov't, trying to secure that avenue, and the terrorists, trying to exploit it. Who will get there first? It probably depends, though I'm sure in many cases, it'll be easier for the terrorist to act than for the gov't to implement programs, and the terrorists will get an attack in before we secure it.
(2) Clam up on possible terrorist strategies, discouraging public debate about it, even, perhaps. For the strategies that the gov't thinks up first, they get a head start. For the strategies that the terrorists think up first, they get a head start. How often will each happen? That depends on the resources each side puts into it, and I think the gov't, if sufficiently determined, can get an edge on the terrorists.
In short, nothing is certain either way, but I would tend toward the side of having the gov't keep at least some things secret. We may need to balance the two sides. For instance, for some avenues of attack, maybe public debate about it would be a good thing, but if there's an avenue of attack that would kill hundreds of thousands and would take some time to secure, I'd say that it'd be best to keep that secret, even at the expense of not thinking up other possible high-casualty attacks.. I'd prefer to gamble on our gov't thinking them up before the terrorists do.
Oh, and let's not forget that we can never possibly secure every possible channel of terrorist attack.. That terrorists will probably always find a way eventually.. We can only hope to slow them down and/or reduce the casualties.