Whether or not anyone should believe that this is an existential threat that needs to be taken seriously depends on whether or not the claim can be justified, and only MIRI is making these specific version for the claim. You are trying to argue “never mind the justification, look at the truth”, but truth is not knowable except by justifying claims. If MIRI/LW is making a kind of claim, a P’S M (as defined by MIRI/LW) that MIRI/LW separately maintains is not a kind of claim that should be believed, then MIRI/LW is making incoherent claims (like “Don’t believe holy books, but believe the Bible).
Whether or not anyone should believe that this is an existential threat that needs to be taken seriously depends on whether or not the claim can be justified, and only MIRI is making these specific version for the claim. You are trying to argue “never mind the justification, look at the truth”, but truth is not knowable except by justifying claims. If MIRI/LW is making a kind of claim, a P’S M (as defined by MIRI/LW) that MIRI/LW separately maintains is not a kind of claim that should be believed, then MIRI/LW is making incoherent claims (like “Don’t believe holy books, but believe the Bible).