it stands out because I can't think of many purely gratuitous scenes like that
In SPN, you mean? Oh, I can... Towel!Sam in "Hell House", workout!Sam in "The Third Man"... It's not that I find it repulsive, or something, but it's the cheap and 'easy' sort of fanservice.

If I thought SPN was doing something wrong or truly offensive I would have stopped watching years ago.
Exactly! Same here. If I don't like something, why to keep watching it.

Thanks again for the link! Maybe I'd argue with the author about a tiny detail or two, but it had plenty of observations making me nod vigorously and was overall very apt.