Reducing dynamic typing's safety to a null set claim is exactly the sort of denigration I'm arguing doesn't make sense. Type doesn't disappear just because you aren't encoding it as a first-class PL design concern.
This discussion is just going to reduce down to a runtime tag vs formal type definition. This particular article is using the term type to mean formal type, and my comment is also under this assumption. Under that definition Ruby does have a null type system. That's not a moral judgement of it's design, it's just a fact that follows from the definitions.
As usual, when freyrs3 says "type" he means something simpler and more specific than what you appear to mean. The whole idea is that "type safety" is both specific and not sufficient to mean anything valuable.
