I don't think they're looking for a specific answer, they ask outlandish & disrespectful questions to see how a player will react to it.
They like to mess with kids depending on their background, so if you're a kid from the hood that comes from a single parent home, they'll say something bad about your mom to see how emotional you get over it. Its fcked up & foul but it lets them know if they're dealing with an emotional immature player that could get in trouble off the field because they can't handle certain situations.
It's a messed up process but if they're going to be paying you millions of dollars they need to know if they'll have to worry about you getting arrested or suspended because you simply can't handle hearing or seeing things you don't like. It's basically a flagging process, if you can't handle some jerkoff GM saying something slick to you in a 15min interview how you gonna deal with the real world after everybody knows you got millions?
I don't agree with it, I think there's better ways to find that out, but it is what it is.