Death threats are different, but insults can also lead to death (there's already an history of suicide as a direct result of sustained bullying)

In a distorted way, insults can have more critical consequences that threats.

No they are not. At least not in the so called civilised countries.

A threat of action is different than mean words. A threat of action is a violent act, where as saying mean things is just rude. A threat of action is a crime in multiple countries.