There must be a clear differentiation between protecting freedom of speech— as the ability to express any idea— and prohibiting acts which are damaging and offensive. Consider the use of two words; ‘gay’ and ‘faggot’. Both words can be used to describe a person’s opinions and ideas towards homosexuals. But the former does not inherently contain an act. It is solely an expression. Within our definitions of freedom of speech, any opinion can be expressed using the term ‘gay’ and it is protected by the principles of freedom of speech.
The latter term, ‘faggot’ is not merely an expression of opinion. It carries with it inherent actions. It is designed to demonise, stigmatise, and abnormalize. Therefore, socially excluding the use of this word is not an erosion of free speech, as the term is not just an expression of speech but outlawing dangerous and damaging actions and behaviour.
In the same way, few would argue that phoning a school and making a bomb threat should be protected under free speech. Although the bomb threat uses words to express an idea, it is inherently an action that should be outlawed. The same applies to political correctness. A politically correct society does not limit free speech, but sets restrictions, as all societies do, on what are acceptable and unacceptable actions.