Yeah, but just say "The person doesn't want their stuff photo'd." Don't make up security reasons for it, as they really don't exist.

That said, don't hear me as just a hater - I don't think I'd want my stuff/setup photographed either, what with embedded EXIF data and all that, but I wouldn't say it was for security, just say, "Nope." None of us on this site have any right to this stuff - it's a privilege. If we want to play we have to play by the project's rules. That goes for pretty much every project on here, and you can tell that because each of them has a different set of rules...