It is logical (remember that logical does not mean that I agree with it or that it's good thinking, just that it's not fallacious) to oppose gay marriage for religious reasons. It is not logical to do so because of the Appeal to Tradition fallacy.
It's politics not debate class though. Things aren't always going to work out logically. This position is an attempt to grant homosexuals marriage rights, while also accommodating traditionalist concerns. It might be logically inconsistent, but the assumption that people who support it are anti-gay is completely in bad faith.
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