I guess I think of moral issues as "leaf nodes" in an argument tree. Things you don't really need further justification for.
You still need to weigh them against conflicting values, but if someone doesn't agree with you that issue X has a moral component at all (or if you disagree whether it's positive or negative), then you are bound to disagree forever.
When an officer asks "why? What have you got to hide?", they've turned it into a practical issue and removed the moral component that I believe exists. That's as ridiculous (to me) as asking why someone doesn't want to be punched in the stomach ("why? Did you just have abdominal surgery or something?").