America will soon decide whether we are a society dominated by hate. The appeal of hate is that it's really simple. It is the aftermath of hate that's such a hard mess.

Complexity is so much less satisfying. But will also have to decide whether we are a society that can navigate complexity; and diversity; and compassion -- and respond in ways that do not make horrific problems even worse.

So many words have been spilled over a question that should be palpably clear by now: Was Omar Mateen motivated by anti-gay hate? Or by the appeal of ISIS? Or was he a troubled loner?

It will not take extensive investigation to establish the basic reality that this was a very troubled man; that he was viciously anti-gay; and that ISIS was a handy flag of convenience for his hatred. There will be more of this, with diverse targets.

Barack Obama is better than your average president at leading us to appreciation of the fact that the world is a frightening and complex place. Obama is way above average at steering us away from hate. Hillary Clinton is pretty good at both -- but she needs to get a lot better, and fast.

Obama's election, less than eight years ago, showed that America, at our best, could avoid hate and embrace our diversity. But at our worst, God help us.

Donald Trump is worse than your average aspiring tyrant at reducing every complex problem to hate. Mateen was an agent of ISIS, all Muslims are potential terrorists, and maybe Barack Obama secretly sympathizes with them.

Trump is close to diagnosably psychotic, and he has the tyrant's gift of enlisting anxious masses in his psychosis.

Let's call out Trump for what he is. He's the flipside of Omar Mateen -- a man driven by hate, a man who would call America to define itself by its hates.

Tragically, the Trumps of the world and the Matteens of the world feed on each other. They need each other. They stoke each other.

To paraphrase the famous words of Pastor Martin Niemoller speaking of the rise of Hitler, first they came for the Muslims and I did not protest. Then they came for the gays, and I did not protest. And then they came for me, and there was no one left to protest.

So we need a mass movement against hate. We need leaders of both parties -- that includes you, cowering Republicans -- to speak out in the spirit of Pastor Niemoller, and stand up against hate before it's too late. We need the mass media to stop using weasel words and to define Trump for what he is. We need every decent American stand up, before they come for us.

There will be a lot more of this -- more loners, more haters, maybe even some real terrorists -- between now and November 2016. Then we will find out what sort of people we are.

We will find out whether the United States will remain a democracy -- a too fragile democracy for sure, a democracy that needs shoring up, but a democracy still.

Robert Kuttner is co-editor of The American Prospect and professor at Brandeis University's Heller School. His latest book is Debtors' Prison: The Politics of Austerity Versus Possibility.

Like Robert Kuttner on Facebook: http://facebook.com/RobertKuttner