The church should not allow itself to be “bullied” on its stance on issues like same-sex marriage and abortion, according to Christian author, radio host and social commentator Eric Metaxas.

Speaking at Scots Presbyterian Church in Melbourne's CBD last night, the American said it was time for the church to stand up and be heard on such issues.

Eric Metaxas speaking with Lyle Shelton, ACL managing director, at the Brisbane event. PICTURE: ACL

“God is saying if you will stand, you have no idea what you can do,” he said, noting that it was time for Christians to “get serious” and stop “playing church”.

Mr Metaxas, whose books include a biography of British Christian abolitionist William Wilberforce and German theologian Dietrich Bonhoeffer who was executed by the Nazis for his opposition to Hitler, has been in Australia on what's been called the 'Fearless' tour for the past week at the invitation of the Australian Christian Lobby and prior to last night’s meeting, had spoken at public meetings in Brisbane and Sydney as well as other, smaller, events.

Responding to reports that he had previously drawn parallels between Nazis and gay activists, Mr Metaxas said he had never made such a claim. Instead, he said he believes there are some parallels between the situation facing the church in countries like Australia and the US and that of the German church in the 1930s where the church didn't speak out against the policies of the Nazi Party.

“What I did say was that the German state started to bully the church, that the German state was beginning to push the church and say 'You can’t believe what you believe'...” he said.

Mr Metaxas said as was the case with Bonhoeffer, who wasn’t afraid of what the Nazis would do, “neither should we be afraid” to speak out on issues like same-sex marriage or the controversial Safe Schools program, saying that the idea that Christians could get a pass on speaking up on such matters was "profoundly wrong".

“When somebody other than God’s anointed tells you to get with the program, you can’t get with the program.”

Earlier, a vocal demonstration of pro-gay activists blocked access to front door of the church, forcing attendees to run what Lyle Shelton, managing director of the Australian Christian Lobby described as a “gauntlet” to enter the building.

A spokesperson for Victoria Police said two men - a 23-year-old man of no fixed address and a 23-year-old men from Alice Springs - were arrested at the protest outside the church for breaching the peace and have been issued with penalty notices. OC spray was deployed during the arrests and the crowd was dispersed a short time later.

Mr Metaxas, who led a prayer that those protesting outside “would come to know Jesus”, told of how he became “dramatically born-again” after God spoke to him in a dream in 1988.

He had written a couple of books about apologetics following his conversion after which his life took a “left turn” and he was asked to write the biography of Wilberforce, a man who spent years lobbying the UK parliament to pass laws banning the slave trade in the British Empire as well as to address other “social evils”.

“(He) us an example of someone who took the Bible seriously and changed the world,” Mr Metaxas said, noting that Great Britain was a “profoundly different” place when Wilberforce died.

Just as in Wilberforce’s time, he said people needed to be educated about what governments were doing in their name.

“God has given us the privilege of living at a time when our faith matters.”

Asked about the US election, Mr Metaxas said he was not as worried about the rise of would-be Republican candidate Donald Trump as some others were but said he would be "really concerned" should Democratic front-runner Hillary Clinton be given the reins, describing her views as "antithetical to American values".