Well, a few years ago milk was half-seriously considered to officially be recognized as a far-right symbol. There was a couple of blockheads who were genuinely using it as a symbol, there also might or might not have been overreaction from the left, trolling from 4chan, or a mix of the two.
As for why it is used as a footbath, I honestly don't have a single fucking clue.

Alright I tried to do a reverse seach and apparently this is part of a photobook by Dany Peschl called "The Disturbation". Here's the story I got from r/cursedimages"