Among millennials regarding this. Second, millennials are definitely not the first generation to have a segment that is borderline communist. There has been a minorly significant portion of the country (5%ish) that has voted for communist type policies since the 1800s. And as much as I dislike Bernie, he isn't Eugene Debbs either. He is much closer to your McGovern types from what I've seen- and he didn't win the Dem nomination on top of that.
Long story short- every generation has a group that thinks communism/socialism will work for them since they are marginalized, except for the 80s-90s youth who got to see the USSR fall on its face firsthand.