It’s a position held by extremists on both sides and the natural ally of extermists, the lazy.

I also find this a bit suspect- the more extreme you are, the more likely you are to have something to hide. The extreme left is well aware of the way communists and hippies were treated through the 20th century, while the extreme right has been subject to a lesser version in the 21st and are very skeptical of intelligence agencies. Moderates seem much more likely to trust institutions and accept the status quo.

I have no idea how to investigate this empirically, though.

I don't really think it correlates with political spectrum at all. Similar to how "hard on crime" has a pretty weak correlation woth partisanship. It really comes down to upbringing, influences, and education on how you perceive data privacy.

In real life, I hear people of all political stripes embracing positions between "nothing to hide" and "the govt can find out my personal info anyway, so why not email it directly to nameless scammers overseas?"

Online it works like most things. Everybody pretends it's a partisan food fight, even if they have to lie.