For me, and many like me (I suspect anyone under the age of 35 who is not evangelically religious) equal marriage is just a none issue.
Equal marriage is the 'shrug your shoulders and say "yeh, why didn't it happen years ago?"' policy.
Equal marriage is the 'we already call civil partnerships weddings, and their results husbands/wives, so what's the big deal?' policy.
Equal marriage is the 'actually, we're mostly not religious so you don't get to tell us what to do any more' policy.
The whole opposition movement is just baffling to me.