Because like it or not, Islam is fighting against you, every single second of every single day. Hamas is one of its faces, al-Qaeda another, and if you allow them to grow in strength and take over previously safe parts of the world (not so long ago, not only Gaza but even Sinai was safe under the Israeli shield) you risk a slow and bloody defeat. One day there'll be suicide bombers on your childrens' public transport, will you be crying out for "peace" then? The PA and Fatah are just another face of Islam and Arabism, though better at hiding it from the naive. Peace with them is impossible, aiming for peace is dangerous if it involves lowering one's guard.
North Korea leader Kim Jong Un hails accord with South as landmark (Reuters)
from the article: Hamas: Abbas selling Palestinians illusions of peace with Israel