I had an airline interview where they asked 'if the one of the Nav lights was inop, and your ready to depart on a night flight, the capt said, go...what would you do?'. There are a variety of answers for this...I answered that I would try to get it fixed, ...they countered it's late at night, you can't...then I countered that I could go to the MEL, let it decide, and hold to it, regardless of what the capt says, they countered(two line capts) that it wasn't up to me to do that, the capt would decide...so seeing where it was going...I stated, that I would defer to the capts authority in a very low key, diplomatic sensisble way. I musted have answered the question right, I moved on to interview with the chief pilot. The right answer: If the capt wants to fly an illegal, unsafe plane, then the FO better agree with it. Same airline that had a jackscrew come apart because the mechanics weren't doing the inspections but just signing it off...