The phrase "vocal opponent" refers to someone who strongly and openly disagrees with a particular idea, belief, policy, or person. They are not afraid to express their opinions and actively argue against it. Full definition
They are also among the most vocal opponents of school choice policies that have been considered by the state legislature in recent years. (empowerms.org)
Teachers have come to expect time off in the summer and have been among the most vocal opponents of extending school years in several locations. (educationnext.org)
So presumably vocal opponents of gay rights would be included. (politics.co.uk)