No one should deny Hillary made campaign mistakes and there were good reasons to dislike her, but the hatred of her was out of this world. When "Lock Her Up" is a repeated campaign refrain enough that a presidential candidate threatens another with the loss of her liberties on a debate stage, you've entered uncharted territory. As Emma Gray points out in Huffington Post, 84 percent of Trump supporters thought she should be sent to prison, while 40 percent said she was an "actual demon." It's not just Trump supporters either. Some (not all) of the Sanders supporters were insane, coming up with all sorts of conspiracy theories about how she'd rigged the primaries, and one official even got a phone message saying she should be lynched because Bernie didn't come out of the Nevada caucus (which he lost) with more delegates. It's one thing for a candidate to be bad and unpopular, but the unprecedented level of vitriol and groundbreaking attacks on Hillary from all sides was more than any male major party nominee has ever faced in recent times.
I actually agree that Clinton being a woman was a net drag on her in the general election. *However*, I also wonder if what you describe above is something that would have happened to any "establishment" Democrat running against Sanders and Trump in 2016 who didn't have a squeaky clean past.
The reason why previous candidates didn't have their opponent threatening jail against them on the debate stage is because previous candidates weren't running against Donald Trump. Trump is willing to break every norm of behavior that his predecessors would not. If John McCain or Mitt Romney had been Clinton's opponent last year, they would not have been saying those same things on the debate stage.
And even in the Democratic primary, I think much of the Sanders critique of "establishment politics" would have proved damaging to any other establishment candidate he was running against. Now, unlike Trump, Sanders wasn't mean-spirited in his criticism. He didn't push the envelope, and in fact, he didn't even run a single negative ad. *However*, as we were discussed in this thread last week, his critique of anyone to his political right is basically the corruption angle--that they're being swayed by big money contributions. While he doesn't get personal about it, I think this does tend to activate many of his supporters into being suspicious of his opponent on ethics grounds. And this probably would have happened with any Democratic opponent of Sanders who was running to his right. I know people will criticize me for quoting Chait again, but I think this is basically right:
http://nymag.com/daily/intelligencer/2016/09/why-cant-america-see-that-clinton-is-flawed-but-normal.html
I do wonder if this is now a long-term feature of intra-Democratic Party split, which will hurt the electability of "establishment" candidates going forward. Will Booker or Gillibrand struggle in a hypothetical 2020 matchup against Trump because the progressive wing of the party will be skeptical of them in a way that they wouldn't have been 10 years ago?
The difference is, Trump pulled the accusation that Cruz's dad assassinated Kennedy out of the National Enquirer, and this was "Trump being Trump," whereas his threat to lock up Hillary was actually something that had currency among his supporters and was built up enthusiastically as a slogan along with more explicitly misogynistic ones like "Trump that B____."
Of course Sanders' valid critique would have damaged any establishment candidate, but it would not have damaged, say Joe Biden, nearly as much as Clinton. Even now, both he and Obama remain relatively popular compared to her. The establishment/anti-establishment distinction is far less important than the amorphous quality of being "liked", and this is where the perception of Clinton as an ambitious, power hungry, arrogant woman really hurt her, while Trump's followers delighted in his arrogance and other foibles, which bounced off him like teflon.
