Say you go up to somebody in public who is minding their own business and start yelling expletives at them and threaten to murder them. Obviously that is making it impossible for them to be free to do what they are doing, and they could certainly have you arrested for that (disturbing the peace or something).
It's difficult to apply this to the Internet because that person certainly has the power to NOT READ the comments from somebody that is attempting to troll them. There are plenty of services in place to ignore these trolls, but instead people let themselves be trolled and then complain about being a victim. This is nothing new, it has been happening since the beginning, but these less experienced users just haven't learned how the Internet works.