Nigel Williams declined to produce business cards for Joanne Lockwood's SEE Change Happen, an organization that is committed to helping others embrace LGBTQ people.
In a letter to Lockwood, obtained by the UK's Sunday Times, Williams wrote, "The new model of diversity is used (or misused) to marginalize (or indeed discriminate against) Christians in their workplaces and other parts of society if they do not subscribe to it."
"Although I'm quite sure you have no intention of marginalizing Christians it would weigh heavily upon me if through my own work I was to make pressure worse for fellow Christians."
Lockwood was distressed by Williams' response.
"I was not expected a lecture. I disbelieved this could happen in 2017. I have been distraught and cried and my wife consoled me," Williams said.
"I think a point of principle is at stake. He wanted to make a point to me deliberately for his own motives. I have been the victim of some discrimination," Lockwood, who is a trans woman, added.
The printer received support from the Christian Institute, an organization that also backed a Christian family in Northern Ireland for declining a request to bake a same-gender wedding cake in 2014.
"It is a fundamental tenet of free speech and freedom of belief that people should not be forced to help promote causes flatly contrary to their own deeply held views," the organization told the Sunday Times.