The fact that so many members of Generation Z went full Trump/Alt Right this election really pissed off a lot of older liberal millenials.
I mean this really depends on how you define
'so many.' We'll only really begin to get good data in 2020, so it could very well be the case that it is just a pretty small but loud minority.
And of course this assumes that if they went on alt-right on a sizable scale, they would vote Republican, but generations aren't rigid anyway, so wouldn't it make more sense for the youngest voters
(18-20) in 2016 to skew more Republican? I don't have data on those particular years but the 18-24 bloc was the most Democratic age group as well.