Freedom of speech wasn't an afterthought. The trick is that, in order to understand how freedom of speech was guaranteed to begin with, you have to deliberately reject a misunderstanding that is at the foundation of hundreds of thousands of pages of US laws and regulations.
"Why declare that things shall not be done which there is no power to do? Why for instance, should it be said that the liberty of the press shall not be restrained, when no power is given by which restrictions may be imposed?" - Alexander Hamilton
The Bill of Rights' whole existence was subject to this debate. One side thought that, without any extra, spelled-out-for-the-slow-children protections for basic human rights, the government would have been more likely to violate those rights. Another side thought that the Bill of Rights would be misleading, confusing people into thinking that the federal government was to be empowered to do anything that wasn't covered by a short list of enumerated limits, rather than understanding that the federal government was to be limited from doing anything that wasn't covered by a short list of enumerated powers.
Sadly, in hindsight both sides were obviously correct.