It is clear that Sanders is not electable or viable in the general election and the rationale advanced by the Sanders campaign is really dumb at best. This quote from the article cited really makes it clear why Sanders is not viable:
That's almost certainly not the case. If Sanders did wind up as the Democratic nominee, tens of millions would be spent by conservative groups familiarizing Republican voters with his record which begins with the fact that he is an avowed democratic socialist. While that's probably enough to take Sanders's Republican support to absolute zero, just in case it didn't, Republicans could run an ad excerpting from this September Wall Street Journal story headlined "Price Tag of Bernie Sanderss Proposals: $18 Trillion." And that would just about do it for Sanders's hopes among Republicans.
Is it possible that even with his socialism and his proposals for massive increases in government spending, Sanders still might be a less polarizing figure than Clinton among Republicans? Sure. But we are talking about slices of an onion in terms of the difference.
There's a case to be made by Sanders against Clinton in a Democratic primary fight namely that she has demonstrated a lack of sufficient commitment to liberal principles during her time in public life. That's sellable to a wide swath of Democrats. The argument that Sanders's is a stronger general-election candidate than Clinton just isn't.
Sanders will not pick up any GOP votes and if that is the basis of the Sanders' viability analysis, then my support for Hillary Clinton is well placed