"This is what the devil is trying to do, to instil into the government, into this world, into society, and it is slowly happening. The sad thing is why a lot of people out there that are non-Christians say bad things about the church, is because a lot of the churches allow those things to happen.
"They say that a man and a man should be able to be married and there is nothing wrong with it. This buys into the theme of pleasing man rather than pleasing God and standing up for the truth."
During his 20-minute sermon Folau also spoke about how his faith had created awkward moments with ex-colleagues.
"You might be the only born-again Christian in that workplace, you might feel a bit awkward with your co-workers because they are in the world and you're not.
We should feel blessed … because God has called us."
Last week Wallaby halfback Nick Phipps blasted Folau for wrecking the Waratahs' season.
Phipps said there were "a lot of (Waratahs) players disappointed in the way it's all gone down."
While another team mate said he didn't want to use the distraction of the Folau controversy as an excuse, Phipps did not hold back.
"I'm extremely disappointed in the stance (Folau) has taken," Phipps told Channel Nine after the latest loss to the Brumbies.
"…but it's obviously something that's very important to him and I can't speak for the rest of the group. But there's a lot of players disappointed in the way it's all gone down.
"It's something that's distracted us from our goal this year to be making finals and it's disappointing that I'm watching the game that I love be picked apart for the last eight months.
"There's so many good stories out there about rugby union and we're not getting to talk about them."