When should you go pre-emptive? This is hard to tell, but if the dialog is not working and our opponent is talking “over your head” without listening, that’s a signal for you, that the diffusing is not working and you must consider to attack. A pre-emptive attack must come without being telegraphed, train to do it when your opponent is processing (thinking).
This is an important timing that is hard in the beginning, but it will be natural when trained.
Don't throw threat displays yourself. Especially in high risk situations. If you look like you are going to attack, it is reasonable for the other person to believe you're going to use physical force.
Remaining calm when threatened with violence takes practice and self control.