evolutionary psychology tells us humans are notoriously bad liars

Does it? I genuinely don't know, since I haven't really studied the subject yet, but it strikes me that if lying didn't work, we wouldn't have developed this whole arms race of deception and social games. You might as well say that the Dark Arts in general don't really work, that humans are notoriously bad at them. Yet my own impression is that if you find something to say that's nice or what the other person wants to hear, regardless of whether you mean it, a lot of people will lap it up if you aren't too crude about it. As has been said elsewhere on lesswrong, it takes effort to detect falsehood, whereas acceptance is natural.