IF you had told me a while back that I’d someday dread, dodge and elect not to return phone calls from a prominent member of the Kennedy dynasty, I would have said you were nuts.

Then Robert Kennedy Jr. started reaching out.

Not just reaching out, mind you, but volunteering to educate me. To illuminate me. That was his tone of voice, somewhat pitying and vaguely patronizing, the one time we talked at length, after he’d left messages and before he left more.

It was important, he said, that we meet.

If we did, he said, he could correct me.

My error?

I had disparaged the alarmists who claim a connection between vaccines and autism and fill parents with needless fears about immunizing their children.

I had sided with the American Medical Association, the American Academy of Pediatrics, the National Institutes of Health and the Centers for Disease Control and Prevention. Kennedy knew better.

Lucky for the rest of us, Jerry Brown doesn’t.

He did something last week that more governors should, signing legislation that compels almost all schoolchildren in California to be vaccinated.

While the state had been fairly liberal in granting exemptions to parents who cited strongly held personal beliefs, the new law insists that there be a sound medical reason for opting out. Some children with compromised immune systems, for example, simply cannot be given the shots.

I imagine that Kennedy was displeased. I’ll confine myself to imagining, because I’m not about to hop on the phone with him again.

He’d just subject me to the scaremongering he practiced in his campaign against the California law.

“They can put anything they want in that vaccine and they have no accountability for it,” he told an audience in April, according to The Sacramento Bee, casting the C.D.C. and drug companies as shadowy peddlers of toxins that ruin children’s lives.

Of those children, he added: “They get the shot, that night they have a fever of a hundred and three, they go to sleep, and three months later their brain is gone. This is a holocaust, what this is doing to our country.”

Their brain is gone?

A holocaust?

If only we had vaccines against hysteria and hyperbole.

It’s tempting just to ignore Kennedy, who later apologized for the word “holocaust,” and his fellow vaccine opponents.

But they keep pressing their case, muttering about cover-ups by the government and “big pharma,” trying to make sure that California isn’t the start of something. (Only two other states, Mississippi and West Virginia, are as strict about vaccines.)

And they’re the epitome of the sloppy talk, selfishness and disingenuousness too common in our debate and society.

One of Kennedy’s comrades in arms is the actor Jim Carrey, whose anti-vaccine theology apparently took form and flight in the church of Jenny McCarthy, his onetime romantic partner and the high priestess of anti-vaccine conspiracy theorists.

A week ago Carrey tweeted: “Greed trumps reason again as Gov Brown moves closer to signing vaccine law in Cali. Sorry kids. It’s just business.”

How predictable: When you don’t have scientific consensus on your side, shout “greed.” Invoke the boogeyman of unbridled capitalism.

Never mind that it’s nonsense. As Phil Plait wrote in Slate last week, there’s odd logic to “the claim that somehow pharmaceutical companies make huge amounts of money on vaccines. Actually, if money were the only reason they did this, it would be far more profitable for those companies to let people get sick.” The profits from continuing treatments would be considerable.

After Brown indeed signed the law, Carrey tweeted that “California Gov says yes to poisoning more children with mercury and aluminum” and that “this corporate fascist must be stopped.”

As it happens, aluminum isn’t present in all vaccines and not all mercury is created equal and equally risky.

And fascist? Carrey has obviously done worship in the church of Robert Kennedy Jr., too.

The anti-vaccine crowd’s bloated language is matched by its narcissism. The whole reason that parents in this paranoid tribe can deem the risk of not immunizing their children acceptable is that they’re counting on other parents to immunize their children and thus create the so-called herd immunity that’s the whole point of mandatory vaccinations.

They want the freedom to do as they please but don’t really want everyone else to emulate them, because then measles and mumps and whooping cough would be immediate threats that eclipse the lesser --- indeed, the imagined --- threat of vaccine-induced autism. The anti-vaccine crowd depends on others to comply so that they can hallucinate.

KENNEDY’S fixation on vaccines goes back about a decade and is in some ways related to his advocacy for the environment. A concern about mercury emissions from industrial plants led to a concern about mercury in thimerosal, a vaccine preservative. He has promoted the idea of a link between thimerosal and autism. The problem isn’t just that most respectable scientists reject any such connection, but also that thimerosal has been removed from --- or reduced to trace amounts in --- most childhood vaccines.

The anti-vaccine agitators can always find a renegade researcher or random “study” to back them up. This is erudition in the age of cyberspace: You surf until you reach the conclusion you’re after. You click your way to validation, confusing the presence of a website with the plausibility of an argument.

Although the Internet could be making all of us smarter, it makes many of us stupider, because it’s not just a magnet for the curious. It’s a sinkhole for the gullible.

It renders everyone an instant expert. You have a degree? Well, I did a Google search!

Vaccine opponents are climate-change deniers with less gluten and more Prada, chalking up the fact that they’re in a minority to the gutless groupthink of the majority.

They’ve learned that as soon as you allege collusion and conspiracy, you’ve come up with a unified theory that explains away all opposition and turns your lonely stance into a courageous one.

Kennedy has insisted that he’s “very much pro-vaccine,” noting that his six children were vaccinated. He’s just trying to ensure that vaccines are safe, he says.

But that means that he thinks that they’re dangerous, and there’s one message above all others to be taken from his rant about mass destruction and from statements like this one, which he made on a radio show in 2011: “I can see that this fraud is doing extraordinary damage to the brains of American children.”

He’s telling parents to watch out. He’s giving them license not to protect children from preventable illnesses.

That’s inarguably anti-vaccine. It’s seriously irresponsible. And it’s especially sad coming from someone whose family’s legend . more Camelot than crackpot . means that he gets crowds to listen to him, lawmakers to meet with him and most of his calls returned.