It seems like a long time ago now, but Jon Stewart used to be an immensely important figure sitting at the place where politics and pop culture meet; he turned Comedy Central’s “The Daily Show” into a hit, becoming the primary source of news for a huge number of (especially young) people by managing to be funny, outraged and sincere all at the same time.

But these days, he’s retired and only emerges from time to time, and because he always delighted more in skewering Republicans, it was a bit shocking to see him go on an extended rant on “The Late Show with Stephen Colbert” about the coronavirus lab leak theory.

This theory has become associated with conservatives trying to prove that former president Donald Trump was right about everything. Yet Stewart apparently thinks it’s the only plausible explanation for the source of the virus.

This provides an important lesson about celebrities: You shouldn’t get your political opinions from them, or your scientific opinions either.

I know what you’re going to say: “That’s just because this time a liberal celebrity is taking a position you don’t like!”

But it’s not that. On the lab leak question, I’m agnostic. Might that be where the virus came from? Sure. Or maybe not. But it matters only for the historical record and questions like “What should international virology lab safety standards require?” As a political question, it’s pretty much irrelevant.

Even though Trump briefly claimed in 2020 (a claim he quickly dropped) that he had lots of evidence that the lab leak theory was true, what did it change? Had we had definitive proof from the get-go that it came from a lab, would Trump’s response to the pandemic, and the resulting death toll, have been less disastrous? Once the pandemic was here, it was here.

But set that aside for the moment, and consider Stewart.

Yes, he has every right to go on as many talk shows as he wants and explain his coronavirus theories. But his attack on expertise reminds us why expertise is so important.

The world is full of amateurs who think they’ve stumbled across some piece of information or logical connection that the people who know a lot more about the subject at hand have missed. There are a thousand unpublished manuscripts titled “Einstein Was Wrong About Relativity” stored on the home computers of people with no formal training in physics.

That’s not to say that experts don’t often have biases or blind spots, because they do. Sometimes, they can be catastrophic. But it’s not because experts can’t be trusted, it’s because something kept them from seeing what they should have, or — perhaps more often — they just didn’t have enough information to arrive at the best judgment.

Celebrities, on the other hand, often find millions of people taking their ideas on things they know no more about than the average person all too seriously.

This isn’t always a bad thing. For instance, politicians in both parties invite celebrities to testify before Congress on issues that happen to interest them, simply because the politicians know the celebrity’s appearance will garner media coverage. It’s the same reason charities want celebrities to appear at their events.

And sometimes, it works. Stewart himself campaigned tirelessly to get Congress to appropriate more money to help first responders who got sick after working at Ground Zero after the terrorist attacks of Sept. 11, 2001; his celebrity helped generate the pressure that forced them to act.

But in that case, the substantive question wasn’t even controversial (everyone said they wanted to do all they could to aid the first responders); it was just a question of whether it was a high-enough priority.

As long as they’re “raising awareness,” no one gets upset; it’s when they take stances on controversial issues that people decide that if that athlete or singer doesn’t agree with them, then he should shut up and stick to the thing that got him famous in the first place.

It feels good when a celebrity you admire agrees with you, and it feels bad when the same person has values that differ from yours. Even though it really shouldn’t; a conservative should be able to marvel at LeBron James’s on-court skills without caring about his politics, just as a liberal should be able to enjoy Scott Baio’s portrayal of lawyer Bob Loblaw without getting worked up about the actor’s support for Trump.

But they’re not experts, and the reason we listen to experts is that they know more than we do. And if they know more about some things than others, then we have to understand where we shouldn’t listen to them and where the limits of their knowledge are.

That’s why it’s problematic when liberals say “I believe in science” as though science always shows you exactly which political decisions to make. Sometimes it does, and sometimes it has gaps that can lead you in the wrong direction. That’s why we need elected leaders who’ll listen to scientists, then make judgments built on a broad range of considerations.

The nature of human existence is that we have to outsource much of what we learn about the world to people we trust. But if a celebrity agrees with you today about one thing, it doesn’t make them any more trustworthy than they will be tomorrow when they disagree with you about something else.

Read more: