A former Federal Opposition leader, Latham made his declaration under NSW parliamentary privilege, which offers him legal protection.
He mounted an astonishing attack on RA, Castle and Qantas boss Alan Joyce over the sacking of the religious footballer, who was found to have broken the terms of his contract via social media comments.
Folau made social media posts that were homophobic in nature, and deemed a breach of his contract.
Latham quoted Castle as saying in a witness statement from the Folau hearing: "I calculated — at least $10 million of annual sponsorship revenue — was at significantly greater risk as a result of Mr Folau's conduct."
He accused Qantas chief executive Alan Joyce and other corporate sponsors of Rugby Australia of forcing Israel Folau's sacking.
Asked for comment, Qantas repeated an earlier statement on the affairs: "We don't sponsor something to get involved in controversy. That's not part of the deal. We expect our partners to take the appropriate action. It's their issue, they have to deal with it."
Latham said Australians were concerned about the loss of religious freedom.
"How in 2019 do we look at Israel Folau and wonder how a football player and resident of NSW has lost his job?
"We're fighting dictatorial corporations who purchase … control of sporting codes. These big corporate chiefs preach diversity ... but they're trying to impose uniformity."
"The head of Rugby Australia is putting a commercial value on the religious freedom of Israel Folau."
Folau intends to argue in his unfair dismissal claim lodged on Thursday that it cost him the chance to become the Wallabies' greatest tryscorer.
He will argue his employment was unlawfully terminated because of his religion.
Folau is understood to be seeking the value of his A$5 million (NZ$5.27m) contract as well as other potential earnings.
That figure could be as much as NZ$10.5m, which if successful would be a massive hit on the finances of RA and the Waratahs.
Folau, 30, has scored 37 tries for the Wallabies, behind David Campese who scored 64.
His unfair dismissal application alleged he had the record in sight, in fact he was "likely" to break it.
"The termination has cost Mr Folau the best years of his rugby career, participation at the Rugby World Cup, the chance to become the greatest Wallaby try-scorer (a decades-old record he was likely to break), and the associated exposure and opportunities," the dispute application stated.