Of all the worthy issues out there today, I'm not sure why Reddit and HN has fixated on this particular one to the extent that they have. But I'm fairly sure that validation-reward effect helps to ratchet up the intensity. You tend to receive a lot votes, likes, etc for commenting in agreement, and I suspect that feedback loop has an impact.
Once again, not speaking in opposition here (God forbid! Pitchforks down!). It's just interesting to watch classic "flash mob" and "moral panic" cycles play out in the new medium.
I wish somebody could figure out how to channel that passion into the larger issues that face us today.
The thing with vaccination is that it's a small thing that really improved our lives. It's what brings down child mortality a good notch with little effort. We can't allow misinforemd people to take this away from us. The parents that don't vaccinate their children not only endanger their children but other people as well. As long as we haven't eradicated a disease, we have to spend ressources on the vaccination.
Success story: Polio 2 is eradicated. And there's only two countries (Afghanistan and Pakistan) where Polio is still endemic. Once these contries are clear, we'll be able to sunset Polio vaccination worldwide.
So while I may deplore inactivity regarding climate change, I'm really happy we're eradicating diseases. And I'm happy people care about it.
By contrast combating climate change is a huge and complicated problem with or without climate deniers screwing things up.
Also, solving climate change is a massive undertaking. Vaccines are a solved problem.
Note well: I am not a doctor. I don't even play one on TV.