He made a bad decision and, as GM, you made a judgement call on that. No problem there. Especially if he made that bad decision "in character". That's all about roleplay.
I'm not saying everything should come down to a toss of the dice. Hell no. What I -am- saying though, is that low intelligence character could just so happen to know this one particular thing even if his player doesn't. At that point it's the GM's discretion as for what to do. Maybe have the player do a skill check at a high difficulty, or not let him have it, deeming the character too stupid, even if the player knows the solution. It really boils down to what kind of history was worked up for the character.
One thing I've seen that alot of nowadays gamers just dont get is this:
You're playing someone that's not you and if you can't "be" that character, then what's the fun? There will be plenty of times that you will know stuff your character doesn't. Take advantage of that and any decent GM will punish you for it.
Therefore, skill checks exist to help the GM keep his players in check. As far as using them in CRPGs though, it's a whole different reason. If you've put alot of points into diplomacy, then you should get more dialogue options, OR, have dialogue options that are best for the situation at hand be highlighted for you since you have high diplomacy and would know the right thing to say. Like the Empathy trait in the Fallout games, but instead of being constant, everytime a new screen of dialogue choices came up, it would roll against your diplomacy skill, compare it to previous successes in the current dialogue tree, and give you the appropriate results.
If you fumbled, well then a bad choice will be highlighted instead of a good choice, or even better, nothing but bad choices will be available just to show how badly you fumbled. Even the most silver tongued person can slip up now and then.
Maybe I am wishing for too much, but that's the way I would want to play. Not the way THEY want me to play. I'll give DL a chance. Nothing wrong with a good action/rpg. I just think what he said in that interview was pretty bunk shit and an insult to the CRPG player in general. That dumbed down shit is for consoles, not computers. Kthx.