I’m not so sure that you are allowed to threaten people as long as you don’t have a prior felony conviction.
No, but they have a much tougher case to prove. This guy is still on probation which means that if he even sneezes the wrong way, or doesn't answer any and all questions humbly enough, more years can be added to his sentence.
When anyone is on probation they have to obey the court. If they displease the court in any way they will be punished. Writing nasty letters to the editor is a great way to get punished. All probationers should be asking is how high the court wants them to jump.