First of all, authoritarian leftism isn't new. The ex-leftist neoconservatives of 2003 who got us into the Iraq War? They weren't the civil rights activists or the hippies. They weren't the ones fighting for desegreation or womens' or gay rights activists. Rather, those people were the communists, Stalin-defenders in the 60s, the left-wing authoritarians who swung right when they were older and richer. It's not really a loss that they went from left to right in the Reagan Era, as they were assholes the whole time.
Anyway, someone being a jerk on Twitter is not the same thing as what the Weather Underground was up to. For good and bad, we're pretty moderate in comparison to the Baby Boomers.
I stopped hating Millennials when I realized that the worst of us are products created by the worst of the exiting generations. You can find anything in any generation, so one bad apple (or few) says little about the generation and much more about those who endeavored to find it. And a young generation will be defined, when it is young, based on the uses that older generations find for it. Evan Spiegel? Lucas Duplan? Miley Cyrus? Justin Bieber? Lena Dunham? They're detestable, but they reflect on their producers, the ones who made their careers, and not on "our generation" in any meaningful way. If you look at the currently small-- and it's small not because we suck but because we're still young and most of us haven't had a chance to get started yet-- percentage (in the arts and business) of prominent Millennials who are actually self-made, the picture is a lot more flattering.