Well the initial response from UL didn’t help.
UL's initial response “In our Contract of Carriage Rule 21, we do have the right to refuse transport for passengers who are barefoot or not properly clothed. More information can be found :

https://www.united.com/web/en-US/con...age.aspx#sec21

Well that response really ignited the leggings firestorm, people/the tweeter universe, ran with the story that all UL passengers wearing leggings/spandex could be barred from flights.
I must say when I first heard this story, I thought, the pax might be non-revs - last ones on, they changed quickly and they didn’t put up a fuss, besides leggings on a flight - really, I see that all the time. The tweet, as Spongebue pointed out, was posted by an uninvolved third party.
But now this whole thing has just blown up, some celebrities have even been quoted as saying the leggings ban was obviously gender discrimination. A guy here is even asking UL pax to wear tank tops and spandex on their flights (I don’t even want to think about that).
Let’s just hope no one writes a song about it. Remember United Hates Guitars https://youtu.be/5YGc4zOqozo