To make people realize the possible consequences of surveillance.
One of the assumptions is that the people aren't completely aware of the extent of surveillance. They assume it's simple as "someone listening to my phone call to my mom" or something as innocent. Something like that hardly has consequences for them, but something like piblishing their private information and data surely has. If they have nothing to hide, they should be all okay with this. If they aren't however... then they should not be supporting surveillance.
To make people realize the possible consequences of surveillance.
If there is a consequence of surveillance that would make these people change their mind, then publishing that information is hypocritical by somebody who thinks it is ethically wrong to expose information that a person might want to have kept secret. If there is no consequence, then the act is useless. If there is a consequence, then these people are using the precisely the mechanism that they argue is the reason we should have privacy.
I wanted the person I was replying to spell this out so I could make the point clearly using their own words, without them getting hung up over how I phrased it.
What you missed is that "nuhhuh, you do, too, here are some things you didn't think about" is not always the adequate response to "I have nothing to hide, or at least I can't think of anything". There's also the matter of public policy, accountability of government, misuse of neutral data by your adversaries, discrimination, and a whole lot more.
