I think that his reply was spot on: Scientists also have a political agenda.
I've spent ten years here on this blog posting about what the science actually says (if you're new to this, you can go here for a high level summary). What I've finally come to realize is that nobody really cares about the science. Sure, I care, but you know how nerdy I can be. Very few other people think at all about the science. They don't want to think about the science. For most people, this is about politics, and Trump cuts right to the heart of this matter: how much legitimacy do climate scientists have?
I have come to the conclusion that the following hypothetical dialog between us and the typical dirty hippy is the right approach:
Dirty Hippy: You're one of those climate change deniers, aren't you? [Note: this is the most droolingly stupid accusation I can imagine. As if anyone believes that the climate doesn't change all the time]
Me: [sneeringly] What do you know about climate science?
Dirty Hippy: The scientists say we're changing the climate. I believe them.
Me: Should you? Are they trustworthy? Do we have any reasons to think maybe they're not?
Dirty Hippy: Um ....
Me: Do you remember when their emails got leaked? Remember the email where they said they did a trick to hide the decline in temperature?
Dirty Hippy: Um ....
Me: This isn't what I'm saying, it's what they said. They said they used a trick to hide the decline in the temperature. You don't know anything about this, but you trust the "Hide The Decline" scientists. Why do you trust people like this? Is it that you don't care how crummy the science is as long as it gives you the result you want to see?
Me: Dude, that's not scientific. It's scienterrific! [it's fun to use your best Tony The Tiger voice here]
His key conclusion as a scientist? Now I have a list of people whose papers I won't read.
The kicker? This crowd is the one that the IPCC relies on for its Assessment Reports - the "scientific consensus".
And at this point you'll notice that I've spent a thousand words saying what Trump said in six. But hey, if you think this has been wordy, go read my post about what the science actually says!