>The difference with atheism or gay rights here is that it doesn't actually harm anyone

This assertion encodes a worldview within it, one that is not shared among a lot (most ?) of religious people, especially in the Middle East. Religious people often assign very high weights to the fact that their religion isn't respected/believed in, and the resulting moral value can be compared with, and often exceeds, material damage to lives and property in their eyes. So the very act of saying "What one does in one's bedroom is none of your business" is itself a topic of intense disagreements. I say this as a closeted atheist in said society who have tried a number of times to play "Devil's Advocate" to atheism and gay rights in my social circles : if only it was as easy as saying "but they don't harm anyone!" and getting people to agree on that.

There are actually analogs to this in western societies (and in every other society I have heard of). Ironically, it's usually the dual to what happens in my soceity : very high sensitivity to anti-lgbt opinions, although the same applies, being anti-lgbt in the abstract doesn't actually harm anyone. Another example is holocaust denial, how does it actually harm anyone ? I don't see an obvious way, a popular stance goes something like "If we allowed people to deny the holocaust, people would percieve it as less serious and it might happen again", but this is overly simplistic and selective, people deny and underplay countless historical atrocities (e.g. the 20th anti- and pro- communism conflicts in Asia,Africa,and South America) and that doesn't automatically make them more likely to happen.

So every society has certain taboos and red lines that you are not allowed to speak against in public (although doing so wouldn't concretely harm anyone), and problems happen when 2 social groups who have different ideas of what should be taboo interact together.

>that convinced them to not get very likely life-saving treatment with no downsides to them

I have several comments on this:

- Cancer and Covid are not comparable in damage, Cancer is uniformly deadly, Covid only so for very specific subsets of the population.

- Cancer is not viral, so whatever happens in the end it will only affect that specific family member and my family, but with Covid you have to balance people's freedom with the threat they pose to the rest of the populations.

Overall, I agree in the abstract that free speech should be restricted in critical expertise-related subject matters, like medical and engineering matters, but the particular case of Covid discourse is such a disaster. Governments and public institutions consistently lied or made up things out of thin air, authoritarians hid behind "The Science^TM" to advance authoritarian solutions to what could be equally solved with voluntary incentive-setting, and overall "The Science^TM" camp just consistently shout louder and assume bad faith more than the reverse. The actual factual subject matter itself is far from settled and much much blurrier than - say - the question of "Does vaccines cause autism", the virus constantly mutates and wipes the floor with the efficiency of the vaccines, lockdown measures are often disastrous and impact far more people negatively than the virus. But there is a certain type of people who will treat the virus as an ultimate demon, to be exorcised at all costs, and they ridicule anyone disagreeing with them as "Science Deniers^TM", and this just becomes exhausting after a while.