If you are a card-carrying human being, chances are that you share the same fear as all other humans: the fear of losing love, respect and connection to others. And if you are human, in order to avoid or prevent the pain, trauma and perceived devastation of the loss, you will do anything to avoid your greatest fear from being visited on you.
The 'pre-emption' versus 'prevention' debate may be a distinction without much difference. The important thing is to have it understood that the United States is absolutely serious. The jihadists have in the past bragged that America is too feeble and corrupt to fight. A lot is involved in disproving that delusion on their part.