I don't agree with him. But it's partly because the whole topic depends upon your definition of "centrism" and I think what has been defined as "left" and "right" on issues has been in the process of change over the last couple decades as the majority of voters became Independents. And now, with radically independent Trump, we will see more rapid change on this front. On any one issue, people will be for or against Trump's ideas on topic and not "left" or "right". Whether this is an up side or down side, it's going to happen, people are going to look at issues outside of left or right boxes.

A good example of this has long been attitudes towards immigration. This issue crosses all kinds of  ideological lines.Traditonally far righties are often anti-immgrant, but lefties who are protectionist about the economy, jobs and social services can also be so. And some GOP are often pro-immgrant, business and Wall Street types who like the invigoration of the best and brightest and hardest working coming to this country, and also those who like to exploit cheap labor.

What I am pretty sure of: I don't think the majority will stop being moderate, or centrist if you like, about individual issues! Most people don't like or want radical change. Even with very serious issues like war, perhaps even more so with those. Passionate ideology is just not part of our majority culture nor even part of many subcultures. Cynicism about ideologues is more like it.