The right to free speech does not require a justification or utilitarian argument. It' a foundational principle. You have the right to communicate how you want, even if someone else classifies your speech as pornographic or political.

If you willingly rationalize free speech, next you'll have to rationalize your right to self defense, and your right to property and on and on, and ultimately you'll find yourself on the wrong end of Hume's Guillotine.