"Why would Jesus have wanted more detail in birth records? How is that possibly connected to his faith, or the religion of his followers?" one user asked.
"Folau needs a social media team to do all his posts for him, you're extremely religious we get that but might be best to stay out of subjects that could easily offend in today's world," said another.
However, others have come out in Folau's defence.
"Load of nonsense isn't it? They are confusing kids so much these days with all these gender nonsense," one man wrote.
Meanwhile, on Instagram, the Waratahs Super Rugby star warned sinners would be going to hell unless they repented.
The image he posted reads "warning" in bold, before listing "drunks, homosexuals, adulterers, liars, fornicators, thieves, atheists, idolaters, hell awaits you".
In a statement released Wednesday night Rugby Australia said the post was "unacceptable" and "disrespectful".
"The content within the post is unacceptable. It does not represent the values of the sport and is disrespectful to members of the rugby community.
"The Rugby Australia Integrity Unit has been engaged on the matter tonight."
The former league and AFL player, now a rugby union star, created tension on social media last year for his stance on homosexuality.
Six months after tweeting his opposition to same-sex marriage, the Wallabies fullback posted on Instagram last April that gays would go to hell.
Folau, who is married to Silver Ferns shooter Maria Folau (nee Tutaia), made the comment in reply to a question on an image he posted on Instagram which showed "God's plan".
"@izzyfolau what was gods plan for gay people??" user Mike Sephton-Poultney asked. "HELL", Folau responded. "Unless they repent of their sins and turn to God."
Folau reinforced his comments after a meeting with Rugby Australia boss Raelene Castle last year, revealing he offered to walk away from the game.
