Our Constitutional right to free speech does not mean that we can just say whatever the heck we want without consequence. If I went around talking shit about a known tough guy and he found me and kicked my ass that's my fault for running my mouth. I'm not going to post pictures in the Boston Globe mocking local gang leaders. I admit that the reaction is way over the top but this person should have known that when you mess with a rabid animal you might get bitten.
Death threats are not a consequence of free speech. Death threats are a consequence of idiots coddling people who make them.
If we take your example and examine what happens we will wee the guy that kicks your ass ends up in trouble with the law, and perhaps in jail. That is how society deals with bullies and assholes who threaten people.
I really do not understand why you are having a problem with this concept. You claim to be a human being with enough intelligence to use a computer, yet you think the consequences of free speech are such that the people who want to kill someone outweighs the consequences of murder.