You're oversimplifying. What we're talking about is censorship that attempts to control what people think and the freedom to express their thoughts.
Neither of the things you just mentioned could be considered the free expression of thought or speech - they are acts that result in the harm of others, and should be prosecuted as such.
Causing a stampede by shouting fire in a crowded theatre is not the same thing as expression of free speech.
Likewise, as disgusting as it is, having paedophilic thoughts is not a crime in and of itself, but searching for, distributing, and downloading CSAM are most certainly criminal acts. And rightly so.