First off, we wouldn't be in missionary if it were all about procreation.. we would be fukking doggystyle only-- like nearly all animals do. The in the dark part makes zero sense. Humans have sex for recreational reasons, but the reason we have those reproductive organs, obviously, is so that we can reproduce.... not so that we can play with same sex body parts.
2nd, religion is older than marriage... and marriage was originally defined by religion and that has been the cause from before recorded history up until recently when the 'gay movement' started making noise.
3rd, not everyone who opposes gay marriage is religious and there are religious fakkits all across American... I've seen gay men in Church.
4th, Gay don't want marriage for 'rights' reasons.... they have always had rights even when certain religious groups, races, ethnicity.. did not have rights. If they wanted 'rights' then they would expand the scope of civil unions and fight that fight. The want marriage so that they can validate their lifestyle and life choices.... and to make it the norm to call everyone against it a bigot.