Aren't all theological claims equally valid?

I think you are correct. I would go further and say that the entire subject of theology doesn't even qualify as a subject at all. If you take any field of study say physics it can be supported by evidence or is vulnerable to falsification. Either way our knowledge of the universe is advanced by just a little bit more. Theology seems to contradict itself it is a field of study that studies the unknowable. Which is impossible by definition. If such a thing as the supernatural exists and there is a god and he has opinions about human sexual behaviour, that is something that is fundamentally outside of physical reality and even if it really does exist you could never know anything about it. So yes I would say you are correct all theological claims are equally valid in that they are all absolutely useless.