Earlier quoted context omitted.
Maybe I'm off my rocker, but isn't this exactly what "white lies"[1] were invented for? You don't actually always have to be 100% truthful with everyone. (That will also serve you badly in other social situations, BTW.) [1] Point being that even if people eventually find out that you did tell them a "white lie", they'll actually usually be very understanding because that's the societal norm and they realize that you…
But can't we decline politely while still telling the truth. Lying seems unnecessary in this situation. I think white lies are more for things like when someone asks you what you think of their cooking and you tell them it's delicious no matter how it tastes.
It's basically plausible deniability (or "denial", if you will) for social interactions... which is at the basis of most of human interaction, if you think about it.
EDIT: Of course, if you're laboring under "Depressive Realism"[1] then all of this is pretty transparent, but if you buy the DR hypothesis then most people actually don't notice this type of thing going on (at the meta level, obviously sometimes they'll discover they've been lied to, etc.).