Yeah I dont know who you have been talking to but most of those young liberals demonizing Hillary are actually libertarian refugees who are just anti-establishment. Such as my roommate. Who used to support Rand Paul and now is a Bernie supporter. Looking at the /r/politics sub on Reddit is not indicative of most liberals. Most actual liberals wouldnt cut off the nose just to spite the face. And the turnout for the democrats is hardly record lows. Maybe compared to 2008, but certainly not record lows. For example, turnout this year in South Carolina was much higher compared to 2004. Plus I know of a number of Republicans who would vote for Hillary over Trump. Such as my parents and some of my friends. And when you have the Senate Majority Leader saying that the GOP wont get behind Trump if he wins the nomination, its clear that they would rather torpedo Trump and have a better shot at winning 2020 (once the anti-establishment candidates have been discredited) than have Trump in the White House who could be a major disaster for the GOP.