When I was 12, my cousin Salina was 15. She was sitting in the back seat of a car with the rest of her family when a truck carrying concrete pipes came around the turn. The trucker had failed to secure his load properly, and the pipes broke loose. One of them smashed into Salina's head. My family has never wept as deeply as we did during the slideshow at her funeral.
The trucker didn't want to kill Salina. We can't condemn him for murder. Instead, we condemn him for negligence. We condemn him for failing to care enough for others' safety to properly secure his load. We give out the same condemnation to the aircraft safety inspector who skips important tests on his checklist because it's cold outside. That kind of negligence can kill people, and people who don't want their loved ones harmed have strong reasons to condemn such a careless attitude.
Social tools like praise and condemnation can change people's attitudes and desires. I was still a fundamentalist Christian when I went to college, but well-placed condemnation from people I respected changed my attitude toward gay marriage pretty quickly. Most humans care what their peers think of them. That's why public praise for those who promote a good level of safety, along with public condemnation for those who are negligent, can help save lives.
Failure to secure a truck load can be deadly. But failure to secure one's beliefs can be even worse.
Again and again, people who choose to trust intuition and anecdote instead of the replicated scientific evidence about vaccines have caused reductions in vaccination rates, which are then followed by deadly epidemics of easily preventable disease. Anti-vaccination activists are negligent with their beliefs. They fail to secure their beliefs in an obvious and clear-cut case. People who don't want their loved ones to catch polio or diphtheria from a neighbor who didn't vaccinate their children have reasons to condemn - and thereby decrease - such negligence.
People often say of false or delusional beliefs: "What's the harm?" The answer is "lots." WhatsTheHarm.com collects incidents of harm from obvious products of epistemic negligence like AIDS denial, homeopathy, exorcism, and faith healing. As of today they've counted up more than 300,000 injuries, 300,000 deaths, and $2 billion in economic damages due to intellectual recklessness. Very few of those harmed by such epistemic negligence have been listed by WhatsTheHarm.com, so the problem is actually much, much worse than that.