The issue about gay marriage is an issue about equal rights. A marriage certificate given by the court allows couples rights. Now all couples are able to marry and have those rights.
This is NOT a religious issue. This is an Equal Rights issue. The government created this issue by giving benefits and privileges to couples who got a marriage certificate. Now you must give all couples, who want those same benefits and privileges, a marriage certificate.
How is this a religious matter? Because you don't like it? I don't like taxes.