Part of effective DIPLOMACY is refraining from threats/insults/attacks/exacerbation. You shouldn't do both simultaeously. Why do we?

That is not true.

Sometimes intimidation is a necessary part of diplomacy. Diplomacy is negotiating favorable relations. This is usually achieved with honey rather than vinegar, though not always. Some people only respect strength and mistake our kindness for weakness.

probably cause people seem to want to do both