....."really? hmmm...."
Here's the thing: when someone is testing you like this (and it can be a gaffer, an AC, a producer, the caterer, you name it) you'd better be 100% confident in what you're doing, or you may begin to feed into that second-guessing yourself.
I've found that if someone is expressing concern about your choices, whether in production or telecine, it can be instructive to hear them out, but not give them any ground (unless they're right, but that's another story). If you're being accosted by a ne'er-do-well, it helps sometimes to just throw it back on them to explain their reasoning- (and then you can politely say, ""really? hmmm...." ;)
If you're really confident in your choices, you should be able to communicate that concisely- if you can't, then certain folks will stomp all over you and your work.
This is an interesting problem, and one that doesn't seem to be discussed too much, and I'd love to hear how other DP's handle it.