I've never heard an anti-vaxxer say things such as "It's God's (or Gaia's) Will that Johnny died of measles."
They believe, wrongly in my opinion, that vaccines cause other medical problems serious enough to justify not using vaccines. To me, that's legitimate dissent.
Given the stakes, maybe GoFundMe did the right thing.
But what's an acceptable threshold of risk?
Because, for various reasons, anti-vaxxing has become a political problem as well as a health problem. Maybe more so.
The political aspect - i.e. GoFundMe being vulnerable to political charges of endangering the public - is probably what drove GoFundMe to institute the ban.
Which leaves other politically charged uses of GoFundMe vulnerable.