They explain their rationale.  They should be heard.  Maybe the news isn't earth-shattering but it is important.

Nice try Michael.  I know it's important to you to see good (and bad) in both candidates and supporters of both candidates. Fact is one candidate is clearly superior and the arguments raised by the other one's supporters don't add up or are largely based on group identity politics.  Read Walsh if you disagree.  Even attacking BernieBros as sexist is a ploy to generate support with destructive group identity politics.

The vast bulk of Walsh's 5-page+ endorsement focused on Hillary's gender and the alleged sexism of some of Sanders supporters along with Sanders' "tin-ear" when it comes to gender matters - e.g., he talks about increasing family leave available to mothers not fathers.  Walsh admitted that she is troubled by important aspects of Clinton's campaign, especially her support for wars and her speeches to Goldman Sachs.  For Walsh, it's clear it boils down to sex.  Her final two paragraphs:

I don’t feel that way anymore. I’ve come to feel passion for Clinton herself, and for what I see as a movement that supports her, even though only Sanders is judged a “movement” candidate. I believe she’s evolved back to be the progressive Democrat she used to be, more progressive than her liberal husband. Some of my feelings remain defensive, but in a warmer sense: I really don’t want to see her abused again. I’m tired of seeing her confronted by entitled men weighing in on her personal honesty and likability, treating the most admired woman in the world like a woman who’s applying to be his secretary. I’m stunned anew by the misogyny behind the attacks on her, and her female supporters, including my daughter. I’m sick of the way so many Sanders supporters, most of them men, feel absolutely no compunction to see things through female Clinton supporters’ eyes, or to worry they might have to court us down the road, take special care not to alienate us lest we sit the race out in November, if our candidate loses.

Of course we won’t do that; we’re women! We’re trained to think about everybody else’s needs first. It’s not just that: women will be hurt the most by a GOP presidency. Naturally, I will back Sanders if he’s the nominee. I promise I’ll eventually feel joy about it—after grieving, if Clinton were to lose again. But if that were to happen, it wouldn’t be because I was too busy protecting my lefty bona fides to say I support her, enthusiastically, this time around. I stand with a lot of women who feel the same way, including my daughter, and we won’t be erased.

Compare and contrast that with Van Den Heuvel who in less than a page notes Sanders is better on Wall Street, militarism, healthcare, and getting big money out of politics and explains why Bernie is the candidate who really can bring about positive change.

Connie Schultz defends Clinton from the charge that she is unwilling "to challenge [the] power structure".  The Benghazi hearings don't provide evidence that she is prepared to take on the power structure.  I do agree that Clinton has done so on occasion.  But, in direct contrast to Bernie's record, Clinton's more often than not reflects acquiescence to the rich and influential and the policies she supports or is unwilling to challenge have led to increased concentration of wealth and economic injustice.  That's what the Neocon/Neolib apology illustrates and that's why the Nation and the Wellesley students and countless others support Bernie.