[andrepd]

It's not just a saying, the pen is truly mightier than the sword.

Hitler never physically dragged a jew into a gas chamber. After 1933 he never shot someone or so much as brawled with anyone. Yet it was only words, his words, his speech, or ink on a paper, that compelled millions of people to commit some of the greatest atrocities in modern history.

Words can obviously be a more powerful thing than actions. In another example, if someone is depressed or suicidal, and they are close to you, you can probably make them kill themselves with words alone, if you choose them correctly.

[cies]

Exactly. Hence inciting violence/hate is prohibited by law in most developed democracies.

[sebmellen]

Hitler's orders had an extremely clear and well-traced direct effect on the physical world, borne out in the tragedies you mention. He could therefore be tried for war crimes. His actions were not free speech, they were military orders. This is not an argument against freedom of speech.

The first thing any dictator does is begin to curtail the rights of their citizenry. The first right to go is the right to free speech.