The state healthcare exchanges doing any kind of targeting and/or marketing, even to 'get people' to sign up for subsidized healthcare, could also be conceived of as unreasonable. I could be wrong, but I wouldn't think their mandate under the ACA contemplates any targeting or marketing of themselves whatsoever—even if it's ostensibly to increase enrollment.
That it feels like there's an implicit assumption that they would (target or market) seems to be part of the problem.
> could also be conceived of as unreasonable
It could also be conceived of as perfectly reasonable. One of the many (some very flawed) purposes of the ACA was to get more people insured, advertising that state-subsidized insurance is available for you is absolutely in that wheelhouse.
If retargeting is the problem, it should be banned across the board, both for public and private ad campaigns.