Where does the freedom to "say what I don't like" end and harassment begin?
In terms of content, you can say whatever the fuck you like about me. In terms of place and time and manner, you can't say whatever the fuck you like on my front lawn, because that's trespassing. You can't say whatever the fuck you like about me in my living room, because if you break into my house I will engage in legitimate self-defense and you will be quickly be unconscious or dead.
You can say whatever the fuck you like about me when we're in public, but if you continually follow me around at some point you are expressing a threat and committing assault. That has nothing to do with what you're saying, though, it applies even if you're silent -- it's the physical presence that's a threat.
You can say whatever the fuck you like about me on the internet or on TV or in a letter or on the phone or whatever. Unless you make a specific threat, and can be reasonably believed to have the means to carry it out, it's not assault. "I'm going to drop a nuclear bomb on Tom's house!" is not a threat, unless you command a nuclear arsenal. "Somebody ought to shoot Tom!" is offensive, but I don't have a right to not be offended, and unless someone is pointing a gun at me at that moment it's not assault or encouraging assault.
A nation with an interest in freedom could handle these cases without any new laws against trolling, using the same legal principles that have existed since the first idiot was prosecuted for mailing a threatening letter. But a moral panic about the 'net is fertile ground for authoritarians.