The American Civil Liberties Union celebrated International Men’s Day by proclaiming its support for “men who get their periods” and men “who get pregnant and give birth.”

The iconic civil-liberties organization used the awareness event, which takes place annually on Nov. 19, to wade into transgender issues and the redefinition of what a “man” is.

“Men who get their periods are men,” ACLU’s official Twitter account told over 1.7 million followers Tuesday. “Men who get pregnant and give birth are men. Trans and non-binary men belong. #InternationalMensDay”

Men who menstruate and gave birth do so because they have uteruses and are biological women.

But Lambda Legal, tweeting similarly Tuesday, offered a different definition of “man.”

“Qualities that make someone ‘a real man’: 1. Identifying as a man. 2. See above. 3. See above. 4. See above,” the LGBTQ-rights group explained.

Forbes contributor Stephen Frost wrote Tuesday while explaining the event’s rationale that “Men, like women, are diverse.”

“Whilst an overriding stereotype of the buccaneering cowboy may persist in some minds, most of us can see from a cursory glance of social media that we now run the full gamut — from super alpha to super beta and all levels in between and around,” he wrote.

Mr. Frost added that “gender fluidity challenges more and more the very notion of binary gender divisions and what a ‘man’ is supposed to be.”

Reaction to the ACLU’s tweet, however, was overwhelmingly negative.

Some reactions include:

“Reality isn’t a thing anymore it seems.”

“The fact that ANYONE will read this nonsense and still give you money is baffling.”

“I get not trans shaming or whatever it’s called, and we should definitely love and accept all people, but this is really silly. It’s possible to love our trans friends and not pretend reality isn’t reality.”

“I remember the good ol’ [sic] days, when the ACLU was about free speech & civil rights.”

IMD was started in 1999 by Dr. Jerome Teelucksingh from Trinidad and Tobago; his birthday was chosen as the celebratory date, UK Independent reported.

There’s no one way to be a man. Men who get their periods are men. Men who get pregnant and give birth are men. Trans and non-binary men belong.#InternationalMensDay