Threats will also be legal. This after all is just a series of noises. To be consistent a libertarian must claim that only a physical violation is illegal. A rapist who threatens his victim with a knife will not be convicted in court unless he physically hurts his victim because he will claim that the knife is his and he was taking it for a walk. Sure, he uttered a few words about killing the poor woman if she did not obey him, but they were just sounds and it is her own fault if she interpreted those noises as threatening.