>>_____k+(OP)
The simplest retort I've heard to "I have nothing to hide" is "then send me a nude photo of yourself." Theres nothing wrong with nude bodies, but it is definitely private. I.e. privacy has nothing to do with hiding wrong/illegal things.
(obligatory disclaimer: a little inaccuracy saves a lot of explanation, but I think this gets the gist across)
>>chacha+hx
The easiest response to this is that I can be OK with a limited audience seeing private information about me in service of higher goals without assenting to unnecessary widespread distribution of the same material.
For example, my doctor can look at my genitals any time he needs to, even if I don't want you to see them.