I'm probably preaching to the choir here, but let's give 'er a go, shall we?
Please read the following as actual reportage. It's not an analogy, a simile or a metaphor. The subject under discussion really is the eating of peas on a Thursday.
Religious group A believe that eating peas on a Thursday is an abomination unto the Lord.
Religious group B, interpreting the same scripture, believe that eating peas on a Thursday is perfectly fine.
Group C maintain that there is no god, and that the eating of peas on a Thursday should be left up to individual conscience.
A large minority of group A petition parliament to have a law passed, making the eating of peas on a Thursday illegal not just for themselves, but for people of groups B and C as well.
Given that opinion on the morality of eating peas on a Thursday is split,* the government looks at research into whether any harm can be shown to accrue from eating peas on a Thursday.
*Yes, yes, 'split-peas.' Very punny. CoughRemcoughigiuscough.
Virtually all medical experts who aren't affiliated with religious group A state that eating peas on a Thursday has no detrimental effect on the human body. In fact, they say, some people who have a particular affinity for peas seem to be a lot happier and less stressed if they're able to eat peas on Thursdays.
Many of the less dogmatic of the experts affiliated with group A state that it's purely a religious edict, and that peas on Thursdays aren't detrimental to bodily health.
Only the small minority of experts who are already dogmatic members of group A are of the stated opinion that eating peas on a Thursday is harmful.
The government weighs the evidence, taking into account possible biases of the various experts, and states that eating peas on a Thursday is legal, but not mandatory. If your religion forbids you to eat peas on a Thursday, they say, then you are under no legal obligation to eat peas on a Thursday. However, they go on to say, no one should be forced against their will to forgo peas on a Thursday.
First make a note of your reaction. Was the government decision practical and sensible?
Now go back and read it again, but this time as an analogy wherein the eating of peas on a Thursday is standing in for same-sex marriage.
Now do you think the government decision is practical and sensible?
If you thought the government was wrong in the first, pea-eating, scenario, I'd be mildly interested in your reasoning—though I suspect you're beyond reason. Try reading it again, imagining yourself as a member of group B or C—or, if you can stretch that far, as a person with a pronounced taste for peas.
If your answer changed as the subject changed, I'd really like you to explain why in the comments. How do the two scenarios differ in principle?