The answer is: because Bernie threatens big corporate interests.

[DanTex]

78. I'm not talking about Democrats to the exclusion of every other voter.

I'm talking, generally, about anyone who would vote for one/some candidates against Trump but would sit home or vote for Trump if it were another candidate.

The point I was making in the OP is that, when it comes to Bernie, such voters are derided as "disloyal Bernie Bros" or whatever, whereas for other candidates like Bloomberg, this kind of voter is heralded as a "moderate swing voter." Which represents an obvious rhetorical bias against Bernie, since at the end of the day, both of those kinds of voters are in the same category of "might vote for the Dem nominee, depending on who it is."

You are correct, though, in saying that it also matters who would drive more opposition turnout from the GOP. So it's not automatically true that whoever can get the most votes in the GE is the most electable.