Even if there were no orphaned twins involved in the politics of early Rome, it's likely the original myth did involve a whore, but the usual uptight types would have preferred the less smarmy alternative. Which sounds more "romantic", being raised by a whore, or being tough enough to survive the wilderness on wolf's milk? Who would YOU want to look up to? Certainly not the sons of a whore.

A lot of myths were probably just really old stories whose origins got forgotten, and with those forgotten origins, the slang and metaphors got taken at face value. Medieval kids would have understood Red Riding Hood's "wolf" to be fully human, but that slang (along with murderers living in the woods) was forgotten by the time of Grimm, and certainly isn't relevant now. Also consider how Gulliver's Travels was meant to be satire, but is now considered nothing more than lame-ass children's fantasy by the general public.

Jeffrey Dahlmer, where we call him "serial killer with cannibalistic tendancies", medieval people would have tagged him "werewolf". Conversely, I kind of vaguely remember reading something about some missionaries, who found they had to tone down the metaphorical "lamb of god" stuff because the tribals started to think Jesus was an actual sheep.