Dustin Lance Black, who won an Oscar for directing Milk - a movie about gay rights, wrote a blog in which he talked about his own experience growing up in churches.
He claims church groups do much good in terms of community, but they are corrupted by the fact they are not welcoming to gay people.
"My hope: that the faithful of America will come to realize that, although not illegal, shutting LGBT people out of the comfort and protection of our religious institutions is un-Christian and immoral," he said.
While the USA recently passed laws to legalise gay marriage across the country, Black says there is still a long way to go to change attitudes.
Many mainstream churches in the USA campaigned against the legalisation, with the main argument being children do best when raised by a mother and father. They said legalising same-sex marriage would go against the best interests of children.
But Black said: "Legitimate religious organizations in our country will never be forced to change their stance on LGBT people, nor should they.
"But for all of our sake, I hope that these institutions will begin to listen, love, and open their doors to my brothers and sisters who seek their comfort and community.
Dustin Lance Black and Tom Daley recently announced their engagement through an advert in the Times newspaper.
With gay marriage now legal both in the UK and the USA, they are yet to announce plans for their wedding.