John Stonestreet regrets the new orthodoxy that doesn't allow any room for alternative voices on marriage.

The speaker and fellow of the Chuck Colson Center for Christian Worldview writes in a new commentary on the BreakPoint website that Barack Obama's decision to support gay marriage opened the "cultural floodgates" in the US and the result is a troubling degree of intolerance, especially in the workplace.

He refers to recent futile attempts at preserving the traditional definition of marriage at state level, and legal cases involving Christian bakers and photographers who did not want to provide services for gay weddings, only to find themselves fighting to keep their businesses in operation.

States like Pennsylvania and Oregon have this week had their bans on same-sex marriage overturned by federal judges.  Earlier in the year, a law passed by the Arizona State Legislature, which would have allowed businesses to refuse service to homosexual individuals on the grounds of "sincerely held" religious beliefs was vetoed by the state's Governor.

Stonestreet goes on to list high profile figures who have been on the receiving end of "smash-mouth, brass-knuckle treatment" over their support for traditional marriage.  They include Mozilla founder Brendan Eich who resigned following a backlash over his support for Prop 8; Duck Dynasty's Phil Robertson who was suspended from his own reality show after criticising homosexuality; the Benham brothers dropped by the Home and Garden TV network after reports of their conservative Christian values emerged; and Miami Dolphins player Don Jones who was suspended and sent on sensitivity training after tweeting "horrible" in response to images on the TV of gay St Louis Rams player Michael Sam kissing his boyfriend. 

"Apparently one cannot even host a home improvement show if one does not also parrot the new sexual orthodoxy," Stonestreet wrote.

He continued: "Sensitivity training? Re-education? What is this, Communist China?" continued Stonestreet.

"In every case, the message to those who disagree with all this sexual 'tolerance' is clear: If you want to keep your job, shut up.

"Apparently the sexual left cannot tolerate even the slightest dissent."

He compared the onslaught of intolerance facing American Christians today to the McCarthy era, the period in the Cold War when the US government hunted down those suspected of 'un-American' activities, often on the basis of little or questionable evidence.

"It amazes me that the media and the homosexual movement, who fought so hard for equality, apparently don't see the rich irony of putting the economic screws to alternative voices," he said.

Stonestreet concluded by calling upon Christians to continue to speak out about God's vision of marriage and human flourishing "despite the obvious and growing threats to our livelihoods".

He qualified this call with a plea to Christians to "speak winsomely whenever possible, making the issue about Him, not about us".

His comments come in the same week as Gallup revealed that increasing numbers of Americans are supporting gay marriage.

New research from the pollster shows support for same-sex marriage at an all time high in the US, with 55 per cent agreeing that marriages between same-sex couples should be recognised as legally valid with the same rights as traditional marriages. Forty-two per cent said they should not.

The percentage in favour has grown steadily in the last decade and figures have turned on their head since 2004, when only 42 per cent said gay marriages should be legally valid with the same rights as heterosexual marriages, and 55 per cent said they should not.

The study also reveals the extent to which attitudes have changed in the last two decades, with figures going back to 1996, when 68 per cent were opposed to legal recognition of gay marriage and only a quarter (27 per cent) supported it.

The increase in support coincides with gay marriage being made legal in states across the US over the last decade, starting with Massachusetts back in 2004.

Support for gay marriage has remained over the 50 per cent mark since 2011.

Read the research in full here