I think that is sort of the point: There are some people within the Wikimedia/Wikipedia community who simply don't even want the bit to be added to the MediaWiki software database structure in the first place, particularly as it applies to adult content. It doesn't matter that this is turned off by default or that it is even optional to put on a page or image and can be removed with a simple edit by an ordinary editor.... there are people in the community who simply don't even want the feature at all ...
With the exception of the "will go to any length", stuff that I've snipped out here, I'm pretty much one of them.
And the reason is simple. Image and web filtering outside of Wikipedia has always turned out to be a coatrack not just for "not showing sexual acts" but for the insertion of political, sexist, racist, or heterosexist bias. Moreover, not every parent shares the same definition of what it's inappropriate to see, you and I might not call "holding hands" porn, but the laws of North Carolina essentially treat it as sexual incitement, and the people behind those laws are going to want that called "adult content." Obviously the Wikipedia community will average a bit more liberal than that, but (a) there's no objective place to draw a line for an adult content image filter, and (b) those discussions are still going to eat a lot of cycles, and will inevitably erode WP:NPOV, Wikipedia's neutral point of view policy.
And, .. where's the real problem? I've spent quite a bit of time on Wikipedia, and sure there's stuff there I don't want to look at. But surprisingly little, and the vast majority of what is actually problematic doesn't stick around inappropriately in articles. Yet Wikipedia still gets a fair bit of whining where you might think there'd be none--the number of folks deeply offended that one of the pictures at kissing involves two men, or did a few years ago, is telling enough. The last thing the encyclopedia needs is an excuse for more of that bullshit.
So, what's really behind this effort?
Hard to say with Sanger, and he does have fair "concerns", but he's got a history with Wikipedia that raises questions about the motivation for this article. For the board, I'd guess there's a desire to some extent for political (or even legal) cover, a natural inclination, I've worked on a non-profit board. It happens.
But many of those of us who actually want to build an encyclopedia with a neutral point of view are against it.
I'm surprised that anyone thinks this is a surprise.