As Hussein Massawi, former leader of Hezbollah, neatly put it, "We are not fighting so that you will offer us something. We are fighting to eliminate you."
This is all anyone needs to know about "why".
Bingo! You would think liberals would take such statements from the enemy at face value. Instead they're angrier at the people defending them from those who want them dead than they are at the thugs who want to eliminate Western civilization. Their screwed up state of thinking is something we'll never get a handle on.
(Denny Crane: "Sometimes you can only look for answers from God and failing that... and Fox News".)