[eesmith]

It isn't illegal, in the sense that no one will be arrested for saying it.

As I recall, it's a bit more subtle. If the workplace continues to allow discrimination based on a protected characteristic then it will be considered a hostile workplace, which is illegal.

Age is only a protected characteristic for people 40 years old or older, which is every member of Gen X.

This presumes that le-mark's account took place in a workplace. On Twitter, about 6 years ago, a millennial wrote “Ok Boomer” to William Shatner, who replied “Sweetheart, that’s a compliment for me”, as Shatner, born in 1931, would have been in the Silent Generation.

That millennial did nothing illegal.