Well it is pure assumption an immaterial deity exists, and defining a deity in a way that makes evidencing it impossible doesn't make the belief more credible, quite the opposite.
Sorry but that is wrong, all claims carry an epistemological "burden of proof." Why would a bare assertion get a pass, just because it created to be unfalsifiable?
again I'd have to disagree, as without objective evidence that is just a bare appeal to numbers, an argumentum ad populum fallacy.
I'm not clear whether this was something you argued for or against, however I see flaws in the reason anyway.
1. The claim a deity is immaterial is meaningless without ant evidence to support it.
2. Creating an unfalsifiable concept doesn't mean the concept has no burden of proof, otherwise we can simply imagine things into existence as and when we please.
3. A consensus is only significant if it based on evidence and knowledge, a bare appeal to numbers is a known logical fallacy, an argumentum ad populum fallacy. So whether there is a consensus or not on the claim, it is meaningless without evidence to support it, and also irrational of course, as is any claim based on a known logical fallacy.