The answer is: First Amendment freedoms were incorporated into the 14th amendment
Gitlow v. New York case happened in the 1920's when a Benjamin Giltow was arrested by the government for creating Socialist Manifesto.
Giltow stated that the Government basically has no right to arrest him because of the free speech that guaranteed by the first amendment.
Later on, the supreme court decided that free speech will be overlooked if it included an invitation to create violence toward other people.