You might be right that it is an implicit threat and as a threat it constitutes verbal assault, but you'd have a hard time making any real headway in court with that, especially in a he said/she said situation. It might be a crime, but it's one which will see almost no prosecution.
If a tweet (or similar) makes a statement of fact, either mark it as "satire" in the body or provide the original source link backing up the statement (see rule 6)
You might be right that it is an implicit threat and as a threat it constitutes verbal assault, but you'd have a hard time making any real headway in court with that, especially in a he said/she said situation. It might be a crime, but it's one which will see almost no prosecution.