'people posting stuff you consider harmful' is not a simple, black and white issue. Anyone who pretends that allowing all opinions has no consequences is full of shit, anyone who claims that tightly policing opinions has no consequences is full of shit.
Like almost everything in life, you will have to navigate a tenuous balance between these two things and you will never know if you got the balance right. You are just a sack of meat doomed to die.
Humans have a vast body of knowledge about how things work. It's a shame its dwarfed by the vast body of knowledge we are completely ignorant of.
Much as scientists managed to be surprised that life had evolved to eat garbage in the pacific garbage patch, it seems some will manage to be surprised that when humans eliminate one source of mortality, another inevitably evolves to take advantage of the ever-growing supply of humans.