The correct answer to this open question is the following.
The controversy of the Scopes Trial affected Americans’ views on freedom of speech in that it limited the free expression of a high school teacher that tried to teach lessons about human evolution.
In 1925, in the case Scope v. State, professor John T. Scopes tried to defend his position and freedom to teach about evolution, in a time when the Butler Act of the state of Tennessee prohibited the teaching of any subjects regarding evolution in the public school system.
So this trial affected freedom of speech due to the prohibition imposed by Butler's bill. Both lawyers made their cases and although in the end, Professor Scopes was not punished, the bill was recognized legal by the state court.