Most people agree that in some circumstances (hiding a Jewish family in your basement during Nazi occupation, for an extreme example) it is ethically and/or morally permissable to tell an outright lie. Fuzzier forms of deception are, of course, fuzzier.
I have often thought that when I get the time to do a proper study on it, the next full-on book I write will be an in-depth philosophical number called "The Good Liar:An Ethical Guide to Misdirection, Obfuscation, and Outright Bull-$#!%". Y'know, have different chapters on different religious traditions and ethical frameworks, establishing when you should and should not bend the truth, untangling the tangled scenarios that may or may not call for fibbing. I think it'd be both interesting and useful.
Of course, my actual current side-project is a motivational/advice thing called "The Paladin's Guide to Life" (follow my Twitter for more information), so TGL may be a ways off yet.
(Sunday night, INT: EB and JH's apartment, JH is returning in his Dick McQueen outfit)
EB: Hey. You're getting in late.
JH: You're awake.
EB: It's nearly three in the morning. What were you doing?
JH: Uh... community outreach.
EB: You're doing that thing where you're saying something that's technically correct but doesn't actually have meaning so that I can't accuse you of lying, aren't you?
JH: Tactics such as that have been employed, yes.
EB: Ugh, never mind.
JH: Alright, Ellen, you wanna know what I was doing? I was out pretending to be a representative from a real estate developer so that I could run an elaborate scam to try to find the man who mugged me, framed me for assaulting him, and then killed a child.
JH: And yes, it was insanely stupid and dangerous and some people did hit me a bit and there was a nonzero chance I could have been recognized and shot by a drug dealer.
EB: I think I preferred it when you were being misleading and evasive.
JH: Also, you were clearly waiting up for me so we could put a final definition on our weirdass nonrelationship, so let's do that right now.
EB: Yep, evasive was definitely better.