"They can not go through one more time the agony of a year ago when Folau's social media comments trumpeting that gays would go to hell, saw rugby lose sponsors, fans and support", FitzSimons said in the Sydney Morning Herald.
The three-times John Eales medallist was warned but not sanctioned by Castle after defiantly threatening to walk away from the game if his strong Christian beliefs were compromised.
Folau was contracted to Rugby Australia and the Waratahs through to the end of the 2022 season. The post also featured a caption from Folau which quoted several fundamentalist Bible verses.
10 News First understands after similar comments Folau made in 2018, Rugby Australia included in his contract a clause about his social media posts.
Israel Folau dives over to score a try for Australia.
The RA and Waratahs statement on Thursday said they wanted rugby to be a sport that unites and welcomes people regardless of their "race, gender, religion or sexuality".
Qantas, the Wallabies' major sponsor, said it is awaiting the outcome of Rugby Australia's review after condemning Folau's comments. We all talk about in sport and in business that culture is one of the most important products of a team.
England prop Joe Marler taunted Folau with some hilarious posts on Twitter, but former Wales fullback Gareth Thomas has taken a different approach.
"Israel Folau has to go, and will go", FitzSimons wrote in the Sydney Morning Herald. "I think that position in particular has changed a fair bit over the years", Green told reporters.
"To everyone who reads it, don't be influenced by his words".
"Be the better person and be YOU".
His latest post (below) lists a number of different sins (homosexuality) and tells followers that "hell awaits".
The 30-year-old has not played in the NRL since 2010, after sensationally quitting the game to play AFL.
"When someone like Folau makes statements like this, it sends a message that members of the LGBT community are less-than and it can have irreparable harm". "We are pleased to see Rugby Australia's condemnation of the comments and will await the outcome of their review".
A stand-out for the Waratahs and on the global stage during his 73 tests, he had been considered crucial for the Wallabies' hopes at this year's World Cup in Japan.
Champion flanker David Pocock is already under a huge World Cup fitness cloud having played minimal Super Rugby this year as he battles a career-threatening neck injury.