I am a Muslim. I created a new account, as some will hold that against me. This is just picking on someone who is too weak, uneducated and inarticulate to be able to defend themselves. Fuck freedom of speech, it's not what this is about. You don't have, and never had, the right to slander someone in order to pick a fight. If I went to a bar, found the biggest and dumbest asshole in there and called his mother a filth…
However, the rest of your post was just poorly thought out, and deserves the downvotes you got, regardless of what side of the issue you're on.
If I went to a bar, found the biggest and dumbest asshole in there and called his mother a filthy whore, guess how much sympathy I would get in court.
You'll get a lot of sympathy. The courts (in America, anyway) do observe a doctrine of "fighting words", which incite irrational emotions in a person such that they lose control. This is analogous to what would happen were the defendent were unable to control himself due to some mental defect.
The question at hand has nothing to do with fighting words. Since the threats are greatly separated in space and time, no excuse about a temporary loss of rationality can be used. The treats against the artist were fully premeditated.
Legalities aside, defending the artist is the morally correct choice. The only way that we can grow as people and as a society -- and this pertains to both technology and to philosophy -- is by questioning our beliefs and our assumptions. Even when we are correct, we need and we deserve to prove it to ourselves. When we are offended, we can examine the injured belief, and the result should be either that we learn that we are wrong, or we verify to ourselves that our belief is true. Either way, we're better off. Do those offended by these cartoons have such weak faith that their faith will be damaged by them?