When trying to point out the inappropriateness of a touchy situation to someone, I try to lighten the mood with a joke. If you can target the joke to engage their "but that's ridiculous!" response, it will help them to realize that's how their question made you feel.

Something like "I tell you what, I'll give you half the answer to that question if you give me half of your salary after you get hired...". Of course, its entirely possible for someone to take that the wrong way, and just assume you are being a jerk.