It's perfectly rational for AI researchers to think consciousness could emerge in a software neural network. If what goes on between your ears isn't consciousness emerging from a network of neurons, it must be magic. So anyone claiming it's impossible to make machine consciousness should hedge that bet. There's a chance it could arrive tomorrow.

On the other hand we've got no idea whether that chance is so close to zero as to be negligible, or whether it's imminent. Just the fact we don't know indicates it's closer to zero. Not having a theory of consciousness is kind of a big architectural risk. It's like not having a theory of accounting when you're making an ERP product. Sure, consciousness in bio neural networks wasn't designed. But it took a few few product revisions to get there.