It would be hard to argue that the bible actively
promotes same-sex marriage, but I think you could reasonably argue that it says nothing on the subject and so leaves it for the church/community to decide.
There are places where the bible gives guidance for heterosexual marriages, but that doesn't necessarily mean that all other marriages are prohibited. Most people are heterosexual, so it makes sense that the bible would talk about marriage in a heterosexual context.
There are also several verses that condemn gay sex, but I think you could make the case that it's not talking about the types of loving, committed gay relationships that we have in mind today. And also, even if gay sex is forbidden, you could still hold that gay couples are allowed to get married and adopt children, but that they should remain celibate. That's rough, but Christians commonly hold that heterosexuals aren't supposed to have non-procreative sex either. For comparison, the American Jewish Conservative movement holds that male-on-male anal sex is biblically prohibited, but all other aspects of gay relationships are permitted. And even though the sexual act is forbidden, it's also forbidden to invade someone's privacy by questioning whether they're doing it.
There are places where the bible gives guidance for heterosexual marriages, but that doesn't necessarily mean that all other marriages are prohibited. Most people are heterosexual, so it makes sense that the bible would talk about marriage in a heterosexual context.
There are also several verses that condemn gay sex, but I think you could make the case that it's not talking about the types of loving, committed gay relationships that we have in mind today. And also, even if gay sex is forbidden, you could still hold that gay couples are allowed to get married and adopt children, but that they should remain celibate. That's rough, but Christians commonly hold that heterosexuals aren't supposed to have non-procreative sex either. For comparison, the American Jewish Conservative movement holds that male-on-male anal sex is biblically prohibited, but all other aspects of gay relationships are permitted. And even though the sexual act is forbidden, it's also forbidden to invade someone's privacy by questioning whether they're doing it.