This is a terrible article.

There are a few things at play, which the author wishes to conflate into a "dumbing down:"

1) The flailing for relevance amongst social conservatives.

2) The failure of No Child Left Behind.

3) The changing media landscape in the United States.

Cherry-picking results for these three trends can give you a trendline, but so can just about anything:

As to (1), the United States is now a country where more states permit gay marriage than don't, where marijuana is steadily being legalized, where gays are explicitly permitted in the military, where socialized medicine is becoming a reality and where prominent billionaires are rallying support against unrestricted gun ownership. Meanwhile, if you're a tea party conservative looking to get re-elected, you still have to find a sop to throw at the "not Adam and Steve" crowd. Behold: tack a genesis verse onto a fossil bill. Which was done anonymously, by the way. And didn't stop the bill from passing, sans Genesis verse, four months ago.

As to (2), yeah, it's pretty terrible. But the schools aren't failing because the kids want to be stupid, or because their parents want them to be ignorant. The schools are failing because the United States ties education to property taxes. It's a fucking stupid system but it has more to do with neoconservative fiscal bullshit of the type McLean's typically spews.

As to (3), yeah, people aren't reading books as much and they aren't watching the news. But to throw out that "and the Internet isn't trustworthy" canard as if it somehow makes your point is disingenuous. We're having to switch from passive news absorption to active news absorption. It's a societal change, not a mark of ignorance.

Wanna take a look at the real trends? Google "belief in evolution over time" or "belief in global warming over time" and get a fistful of graphs that indicate the exact opposite of the article: more people believe in evolution this year than last year, and more people believe in anthropocentric global warming this year than last. Substitute pretty much any two years and you'll see the same result - the arc of history is long but it bends toward enlightenment.