I would down four shooters of portofinio with him, and hide his car keys, then go out in the front yard and puke with him, till he passes out... put him on the couch, and talk sense into him, when he is at the disadvantage of a rather severe hangover for the next 18 hours... after he sleeps it off.
By then, the shotgun would be "missing" and we would be going out for beer and more pizza...
After a few days, he would definitely realize he was better off, without her...
LOL, perfect answer. Point being, you lie to the MF instead of letting him do something you'll both regret...thus, we see that simply saying "lying is bad" is adequate for children or the untrustworthy, but in the real world it's not so cut and dry.
It's but a small leap then to a battle situation, and since taqiyya assumes that all the infidel are actively trying to destroy the faithful (body and soul), if what they say is true then what's wrong with talking out both sides of their mouths?