I think you can. The burden of proof lies with believers in a historical Jesus, to produce evidence of his reality. The burden of proof equally falls on the Doherty etc mythicists to provide evidence for their suppositions. It may be that both fail this test. Thus, neither a real Jesus nor a mythical Jesus (in the positive and elaborate Doherty sense) can be established. We are left, as you say, with legend; that is, with stories which can be shown to have circulated at various places and times.
But that is what myth actually means--
any traditional story (Bulfinch's Mythology (1855-1863); Remsburg, John (1003)
The Christ; Kirk, G.S.
Myth: Its Meaning and Functions in Ancient and Other Cultures. Berkeley: Cambridge University Press, 1973.; Kirk, G.S. "On Defining Myths".
Sacred Narrative: Readings in the Theory of Myth. Ed. Alan Dundes. Berkeley: University of California Press, 1984. 53-61.)
The story that Christopher Columbus sailed west to prove the Earth was round is as much a myth as the stories of Heracles 12 labors is. IMHO Remsburg explained is best:
"But what do we understand by the term myth? Falsehood, fable, and myth, are usually considered synonymous terms. But a falsehood, a fable, and a myth, while they may all be fictions and equally untrue, are not the same. A falsehood is the expression of an untruth intended to deceive. A fable is an avowed or implied fiction usually intended to instruct or entertain. A myth is a falsehood, a fable, or an erroneous opinion, which eventually becomes an established belief.
While a falsehood and a fable are intentional and immediate expressions of fiction, a myth is, in most cases, an unconscious and gradual development of one.
Myths are of three kinds: Historical, Philosophical, and Poetical.
A Historical myth according to Strauss, and to some extent I follow his language, is a real event colored by the light of antiquity, which confounded the human and divine, the natural and the supernatural.
The event may be but slightly colored and the narrative essentially true, or it may be distorted and numberless legends attached until but a small residuum of truth remains and the narrative is essentially false. A large portion of ancient history, including the Biblical narratives, is historical myth. The earliest records of all nations and of all religions are more or less mythical. "Nothing great has been established," says Renan, "which does not rest on a legend. The only culprit in such cases is the humanity which is willing to be deceived."
A Philosophical myth is an idea clothed in the caress of historical narrative. When a mere idea is personified and presented in the form of a man or a god it is called a pure myth. Many of the gods and heroes of antiquity are pure myths. John Fiske refers to a myth as "a piece of unscientific philosophizing," and this is a fairly good definition of the philosophical myth.
A Poetical myth is a blending of the historical and philosophical, embellished by the creations of the imagination. The poems of Homer and Hesiod, which were the religious text books of the ancient Greeks, and the poetical writings of the Bible, which helped to form and foster the Semitic faiths of Judaism, Christianity, and Mohammedanism, belong to this class."
Even if we limit ourselves to Remsburg's historical myth above we still have problems with Jesus. In fact while Remsburg felt the evidence showed the Gospels account fell in the "narrative is essentially false" end of the spectrum he also felt there was just enough to show there was flesh and blood Jesus in the 1st century.
The problem is if the Gospels are an essentially false narrative they tell us NOTHING about the flesh and blood Jesus in the 1st century--in other words the Jesus they describe is effectively non historical just as King Arthur and Robin Hood are.
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