I would say it started with the tea party protests. Everything about them was a protest looking for an excuse.

The Tea Party was hijacked by the Republicans, who attempted to galvanize American racial, xenophobic and anti-leftist fears against Obama in predictable race-baiting fashion. They failed to prevent a second term, but Trump's populism capitalized on the seeds of white rural discontent, reactionary fear and paranoia that they planted.

I think all of this is the result of the presence of a Black liberal (not even a leftist, mind you, but Stalin incarnate as far as the right was concerned) in the White House causing a cascade failure in American culture, and it's kind of beautiful to see.

I would put it 7 years ago, at least with media and aggressive narrative crafting against certain groups.