You don't get to state this as fact just because it helps your argument. I assume you're well aware people on the other side consider sexual orientation to be inherent, rather than a simple preference.
If it turns out that risk preference or mobility preference is also "inherent", would that make Obamacare or mortgage subsidies/know your customer laws a violation of civil rights?
As an aside: I don't think you're comparing homosexual relationships to bestiality, but you're getting close. I hope you understand why this could be offensive and non-productive in a conversation.
If you must know, I'm pro-gay marriage and against all civil marriage. And I have no position on the current issue.
What I meant is that I agree marriage is a preference, but only if there are no additional benefits or rights bestowed (by the government) upon those entering the marriage.