Threatening to throw someone in jail if they insult a politician IS a restriction of free speech. How else do you restrict free speech? They can't install blocking devices inside a person's vocal chords that prevents the speech from even occuring.
This is like saying speeding is not restricted because people can still push the pedal beyond the speed limit. Of course they can! But there are state enforced consequences for it, which means that speeding is illegal (restricted).
The founding fathers studied the laws and constitution of other countries all too well and knew exactly what NOT to do and warned against fuhrious fatties. Everybody says America sucks but are still fighting to get here (legally or illegally). Cause it sucks so much!