It's not their job to talk nice and use diplomacy. It's their job to advance the policies of the United States. It's their job to avoid war by making sure that our enemies know that doing things we don't like will result in an extremely negative consequence for our enemies, up to and including war and the utter destruction of said enemies.
Liberals have made everyone think that the job of the State Department is to talk nice and be "diplomatic" because if the State Department acts in this way, our interests are thwarted rather than advanced.
The State Department is there to act in our interests. There is no reason to have a State Department if they are inactive. We gain nothing.