The letter also talked about tennis player Casey Dellacqua - who has two children with her same-sex partner Amanda Judd - saying that children born into female same-sex couples will always have questions surrounding their "identity and background."
Dellacqua responded by posting a photo of the article to Twitter, writing, "Margaret. Enough is enough."
Sam Stosur then reposted Casey's tweet, writing, "Proud of you Case x."
"Look, I think everyone can have their own opinion. I don't agree with Margaret's opinion," Stosur said at the French Open in Paris, as reported by ABC.
"That's why Casey was, obviously, very adamant about that and I wanted to support my friend and that's why I sent out my first tweet in a very long time."
"And, look, it's just not something that I agree with. I think we definitely should have it (same-sex marriage) in Australia."
Stosur went on to say she didn't think Margaret Court Arena would be renamed, but that players may choose to avoid it during the Australian Open.
"The court's named Margaret Court Arena because of what she did in tennis, and that's why basically. But I guess we'll cross that bridge when we all get down to the Australian Open next year and (see) who wants to play on Margaret Court Arena and who doesn't, and we'll go from there."