And like all stereotypes, perpetuating them doesn't really do much of anything but be an annoyance, regardless of how much source validity may or may not be present.
And yeah, dude, it happens way more than you might think. We are, it seems, responsible for literally everything wrong with the state of the country--the deficits, the recessions, the market rate drops, the hyperinflation, all of it's the millenials' fault. Because a lot of us are bitchy with smartcars and weird haircuts. Those things definitely totally correlate. Apparently.
Perhaps you've just been lucky to have more surroundings of reasonable conservative/previous gen. groups than I have, I suppose. Gotta a whole slew of "young people suck and ruin everything MAGAMAGAMAGAMAGAMAGA!" folks around here.
Also, consider the definition of warranted less literally and more based on situational context.
Is a millenial being a stereotypical shitlord? Then call them on it. With my fucking blessing.
Is a millenial simply in your presence and bothering you with their mere existence regardless of how they're actually behaving? Then shove it.
Three guesses which one I deal with more.