pro= to be in favour of anti= against pro -marriage = to be in favour of marriage anti -marriage = to be against marriage

Suffics "pro" means "for" which leads me to the idea that "pro-marriage" is an adjective describing people who are in favour of getting married.

This is when someone agrees with Marriage Equality, in this case I assume it is Marriage Equality for Gay/Lesbian individuals. If you are pro marriage then you believe that Gay/Lesbian individuals should have the right to marriage. Hope this helps :)