That's a complicated topic. To me it's not a clear-cut case. There are very good objective reasons why procreation between close relatives is not desirable and thus sex and marriage between close relatives is illegal - namely - it produces offspring with mutations that entails suffering to the offspring and society by extension. No objection of that sort is available for gay marriages.
And that proves that gay relationships are fundamentally different than what has been called a marriage since time immemorial. So, if one is taking procreation out of the equation for marriage, it changes what a marriage is in a fundamental way. So, for example, using the same arguments that the pro-gay marriage crowd uses, then there is absolutely no longer a reason to deny marriages between close relatives if, say, the relatives undergo surgery to prevent them from having kids. Is there?
...But if anyone stills does object to those types of marriages even with child-prevention surgery, then perhaps they can understand why I do not agree with the arguments of the pro-gay marriage crowd.
To be clear, in most respects I don't object to gay rights at all. I didn't object to civil unions... if the state wants to create a legal way to bind people together for those who have relationships different than [traditional] marriages, then that's perfectly fine. But such things should be open to ANY two people (siblings, very close friends, etc), not just those who have homosexual relations with each other.
Anyway, I've been over my views here before, so I'm pretty sure expressing my views again now isn't going to change any one else's opinion.
On the other hand, I have never seen a good coherent secular argument as to why gay marriage should be illegal.
Because it's not a marriage. It's an imitation, which is similar in some ways and different in other. Or putting it another way and to use your language, I have never seen a good coherent secular (or other) argument as to why gay unions should be called marriages.
Of course, what passes for a "good argument" is in the eye of the beholder, isn't it?
Well, I didn't call you [a bigot] since I can't know your motivation...
Sorry, I guess I was still in "reply to One Brow" mode, and thought you were agreeing with his opinion.