Don't feed the trolls.
It's advice always better heeded than not, but one of Australia's immunisation experts says it is particularly important when it comes to vaccine deniers.
University of Sydney Associate Professor Julie Leask says the trend towards collective moral outrage about people who don't vaccinate their children risks making the problem worse.
"Calling them things like 'baby killers' does nothing for this issue, and I think it further polarises people," she said. "I don't see any good evidence that just shouting down opponents actually works".
And she would know. Her own grandmother was anti-vaccination and said "it was the worst day of her life" when Professor Leask's mother decided to get her children immunised.
Yet Professor Leask has found most people who don't get vaccinated don't fall into that category of hard-line, science-rejecting refusers.
Only about 2 per cent of parents are registered as "conscientious objectors", and even then about half of them will give their children some vaccines.
Among the other 8 per cent or so of children who aren't immunised, the biggest group are children who have other reasons, such as being born overseas, being from a disadvantaged background or being in out-of-home care.
About 3 per cent are not up-to-date because they have safety concerns.
Writing in the journal Public Health Research & Practice, Professor Leask says it's unrealistic for us to spend our time and energy trying to rid the world of the hard-line 1 or 2 per cent.
"As long as vaccination has existed, there have been such activists, just as there will always be a minority who stand outside the mainstream, reject orthodox medicine and its interventions, mistrust government and value natural health," she wrote.
Most parents aren't so silly to just unquestioningly absorb the claims of anti-vaxxers, Professor Leask said, but they are likely to be put off by dogmatic arguments and aggression.
"There is a push for greater patient decision-making in health generally, yet we are continuing to revert to this model that says 'don't listen to them, listen to me', but that isn't responding to their needs," she said.
Perversely, going to great lengths to "bust" myths propagated by vaccine deniers also risks exposing people to doubts they would never have come across anyway.
"It creates a very harsh environment, and makes people get the sense that there is a greater debate than there is actually," she said. "It raises the awareness [about issues such as the measles vaccine scare campaign run in the 1980s] among a whole new generation of parents who might not otherwise have heard of it".
It also diverts time and energy away from talking about things such as how we can better target children who are missing out, or asking governments to invest in things such as a national 'whole of life' immunisation register, which experts have been calling for for years.
Perhaps the problem is deep down we all really just like hating anti-vaccination types? After all, it's pretty much the magic formula for an internet outrage storm: little babies being put at risk by foolishness, silly claims that are easily dismissed with basic science, and a high level of social reinforcement from the majority of your friends and colleagues, who, like you, don't believe that magic water or spine adjustments are a possible cure for pathogenic bugs.
But what's it all for? "Publicly adversarial debates are unlikely to convince [doubters] to vaccinate and may merely serve as catharsis for the converted," Professor Leask wrote.
In the end, it was the facts that convinced her mother, and a gentle word from her GP after her son was hit in the head and at risk of tetanus.
Professor Leask says she loves her family, and would never want to see them treated the same way we talk about some vaccine refusers, let alone to think of children being banned from childcare and parents shunned.
"I'm concerned this strategy merely punishes the children for the decisions of their parents," she said. "Do we really want to live in a society that condones stigmatising a certain group of children and their families because of the way they behave?"
