Her wording may not have been ideal but I don't have a problem with mocking an "Asexual day of visibility".
Plenty of people aren't interested in sex for a variety of reasons. Like a previous poster mentioned, many post menopausal women don't want sex. People who take some SSRIs or blood pressure medications have absolutely no interest in sex.
But to make a single characteristic into an identity that requires a day of visibility is kind of wanky. Kind of like when vegans go on about being vegan or people who do cross fit can't shut up about cross fit.
What's next? "Outie navel Day of Visibility"? "Can't pull off a hat day of remembrance"?