Former nine-time Wimbledon champion Martina Navratilova has been taking heat for an op-ed published over the weekend, where she argued that allowing transgender female athletes to compete in sports against biological women is "insane and cheating."

LGBTQ advocacy group Athlete Ally quickly gave Navratilova the boot from its advisory board over her comments, despite the fact that she was one of the first worldwide athletes to come out as homosexual and has defended gay rights for decades.

Now, a gay journalist is slamming the organization for its treatment of Navratilova, whom he calls "one of the greatest LGBT pioneers of the 20th century."

What are the details?

Investigative reporter and best-selling author Glenn Greenwald has come to Navratilova's defense on Twitter, sending out a series of tweets scolding Athlete Ally for its "pathetic" actions against the tennis legend and reminding followers of her trailblazing history.

Greenwald, who is also gay, wrote that Navratilova "has fought more & sacrificed more than all of those now trying to marginalize her combined: at a time when these causes had very little support. Punishing her for raising questions is shameful."

The journalist went on to cite examples of how Navratilova "revolutionized feminism in sports, LGBT equality and trans visibility," and slammed those now attempting to paint the tennis star as "an enemy" of the cause.

Anything else?

Twitter users attempted to argue with Greenwald's points, but he pushed back, telling one critic, "Martina has more courage and has done more for the cause of LGBT equality (in) her toenail than you've done in your entire life."