::Because the particular facts indicate that it's already RS in this particular case (no matter how one might generalize), especially if other RS are treating it as RS, and we should be transparent to the reader about where material originates.  For my part, I don't support the laundering sources through other sources doctrine which instead of seeing the additional coverage as adding incrementally to the argument for inclusion, sees it as effectively turning water into wine.  The story is ultimately just as dubious as the original source if there is only one source.  If laundering actually works, then we as Wikipedians ought to be trying to develop the same sorts of reliability assessment skills the launderers have so we can make the same sort of skilled assessment should a launderer not be immediately available.  Show me someone who cites a primary source for whom it's usually just a matter of time until secondary sources cite in turn and I'd call that someone a presumptively astute judge of both reliability and notability.  Instead of developing and respecting those skills I see editors not bothering to consider the plausibility of what's claimed and instead making blanket judgments about what is or is not RS without concern for whether the judgment is shown to be sound over time or not.  I for one, am opposed to using questionable sources PERIOD when what makes the source questionable is hidden from the reader.  Letting questionable sourcing go if it flatters someone is a double violation of both RS and NPOV in my books.  I note that you contradicted yourself by saying you are opposed to "...assertions about living people" and then saying "this goes as much for" someone who is dead.