Why are Millennials Retarded?

My peers don't pay attention to anything important.  They will latch on to an idea that makes it look like they care about something important, but once that topic has depleted the maximum FB likes and RTs it can, it's over.  They walk into the bathroom with their new outfit, make sure the lighting is right, then snap a selfie in the mirror.  I suspect the Men In Black exist and they started putting their memory-correction devices into all new smartphones.  "Whoops, looks like no one cares about that thing anymore.  Let's go take a selfie. *flash* Wow, look at all the likes my selfie is getting".

 Here's a recent example.

My FB peers were recently supporting Bernie Sanders.  Everyday I saw pro-Bernie stuff.  I it'd be a disaster to vote another Marxist into office, but at least people were interested in arguably the most important non-personal decision they can make in their lives:  Who is going to make decisions on behalf of the ENTIRE country for the next four years?

I went back and forth with these people, happy to engage in dialogue about why socialism is a horrible idea.  Mostly I got contrived rhetoric and links to articles 95% of them didn't read, but at least there was a discussion.

When you looked over the barren, grey plane of dust and wind that is typically social media, you could see a tinge of green -individual buds slowly struggling out of the infertile soil - until it almost looked like a field would finally produce the fruit of mental labor.  And then Bernie endorsed Hillary Clinton and fire-bombed the whole goddamn thing.  You can still see remnants of ash floating around, reminding you of the fruits that could have been, but it looks like the dust will settle - back to the barren wasteland of fake outrage and societal degradation.

I have a few theories, but I'd like to know, why are they so retarded?