"Fixer Upper" stars Chip and Joanna Gaines have come under fire after it was revealed that their pastor, Jimmy Seibert, of Antioch Community Church in Waco, Texas, is opposed to same-sex marriage.

The controversy began when BuzzFeed resurrected a sermon by Seibert in which the pastor - who described the Gaineses as "dear friends" in a recent video - expressed a belief in traditional marriage and referred to homosexuality as a "sin".

"God defined marriage, not you and I. God defined masculine and feminine, male and female, not you and I," he said in the sermon delivered in June 2015, on the Sunday after the Supreme Court legalized same-sex marriage in all 50 states, as transcribed by BuzzFeed. "Truth No. 1: Homosexuality is a sin. The lie: Homosexuality is not a sin."

While believing same-sex marriage flies in the face of God's commands, the pastor he urged compassion for those with same-sex attraction, as "the statistics say that 90% of people who are in a full-blown homosexual lifestyle were abused in some way. Physically, sexually, mentally."

He added, "You can lovingly, carefully bring them back to Scripture, be compassionate in the journey. And help them direct their passions rightly to how god created them."

The pastor also dismissed the notion that it's impossible for members of the LGBT community to change their sexual orientation: "We can change, contrary to what you hear," he said. "I've worked with people for over 30 years - I have seen hundreds of people personally change their direction of same-sex attraction from a homosexual lifestyle to a heterosexual lifestyle. It doesn't mean they don't struggle with feelings, it doesn't mean that they aren't hurting, it doesn't mean it's not challenging. But they have chosen to change. And there has always been grace there for those who choose that."

The Antioch Community Church's website also states that marriage should be between a man and a woman, according to Buzzfeed.

US Weekly reports that Fixer Upper viewers have started calling for Chip and Joanna to clarify their stance on same-sex marriage, with some threatening to pull their support from the show.

"If Chip and Joanna Gaines end up being anti-LGBT, I am cancelling my mag subscription and ignoring their show," one tweeter wrote.

In turn, Chip and Joanna, outspoken Christians who have yet to feature a same-sex couple on their hit show, have not yet responded to requests for comment about whether the couple's beliefs align with their church's.

However, in the past, the couple have said their faith drives everything they do - from the way the conduct their show to how they raise their four children.

"Our family has made a commitment to put Christ first, a lifestyle our parents modeled for us very well. They showed us how to keep our marriage and family centered around God," Chip said during an interview with The Billy Graham Evangelistic Association.

Joanna echoed the sentiment last April during a video for Baylor University in which she discussed her testimony and how she seeks to use her platform to share her faith. She also emphasized the importance of "not believing the lies" and focusing on the truth of the Gospel. 

"I can look back now on the pattern of my life and really believe God has a purpose for me, but He also has purpose for you," the mother-of-four said. "Let God speak into your life...Let his father heart come and say, 'This is what I have for you.' I think that's the key - not believing the lies, fixing our eyes on Jesus, and walking in the truth."

Ironically, in his sermon, Seibert issued a warning to business leaders - like Chip and Joanna Gaines - who may face backlash for their beliefs.

"You will have to be clear about who you are," he said. "And you will have to be willing to stand to lose even a deal or two or 10 or even lose your business. But if you're not clear, you will have no leg to stand on down the road. If you think you're going to get away with it in the short run, I promise you won't in the long run, because the spirit demands submission."

"We're being called to a higher calling," Seibert says. "A greater compassion and love, but a greater clarity than ever before. Because it is coming now. Starting Monday morning, we will not have the option anymore.

"And with that," he said, "will come persecution."

As earlier reported, HGTV - the network behind "Fixer Upper" - famously scrapped plans for a reality series, "Flip It Forward," in 2014 after it was revealed that the stars of the show, Jason and David Benham, opposed abortion and same-sex marriage due to their Christian faith.