You really should add a fourth- the principle of induction. You also misinterpret my premise- it is not that nobody could possibly disagree, but that the ideas could not possibly be false, even under an Evil Demon argument.

The problem is the same as the Isolation Objection to Coherentism- that if there is any actual correlation to reality, it is merely by chance rather than through actual evidence. This is because both groups have no basis for their assumptions.