Aside from that, there's an important difference between expressing an opinion, and creating an atmosphere and culture of hate and/or violence.
There are things you're not allowed to say because they endanger lives, like threatening people, blackmailing people, or slandering people. Spreading intolerance and hatred directed at specific demographic groups has also been shown to endanger those people, so banning that is absolutely defensible.
>Because Voltaire's age was so peaceful and didn't have those things?
Voltaire wasn't a youth bullying youth to the point that they killed themselves.
Voltaire wasn't a man sitting in his living room sexually harassing and shaming women in an organized effort after they are selected as a target by some random person online for blocking them after receiving dick pics.
Voltaire wasn't encouraging anonymous strangers on the internet to make death threats to high profile persons.
(Voltaire didn't said it exactly, it's a later quote. But he said words to the same effect, and it's by itself a good quote).