Indeed, the point about Admiral Hanson was that he didn't really believe
in the Borg, and e.g. dismissed the threat posed by Locutus. The point about the Hansens was that they did believe. We could plead "poetic justice" or whatnot when Granddad Hans*n dies because of his lack of faith, but that's really silly.
Besides, Hanson vs. Hansen is a bit like Ivan vs. John, or Cat vs. Dog, or Night vs. Day. If you spell it with "e", you have Danish or Norwegian roots; if with "o", it's more a Swedish thing. And you don't
go telling Vikings that they all look the same to you!