Really very confused by this op.
It seems to be trying to make the case that bashing Hillary is fine and dandy because “those of us on the Bernie side have legitimate criticisms of Hillary” but expressing concerns about Bernie, in particular about his electability and how “socialist” will play in a general election with severe Swift Boat style tactics being used, or otherwise stating that he is not the best current option, is disallowed as it might “depress turnout” … his supporters are that fragile I guess.
It does not make any coherent sense. And if anything this has been a remarkable low (not zero) negative attack campaign so far with the negativity from Sanders supporters far outpacing the negativity from the Hillary-side to my experience. Mostly Hillary supporters are expressing concern that Sanders would be ineffectual if elected, concerns that his plans are unrealistic, and worry that he may be unelectable in the first place, which are all issues that are very reasonable to discuss and to consider. Really those are polite critiques to what Bernie’s people say about Hillary and what Bernie himself clearly implies. Which again, by any standard of past elections, is pretty mild itself.