Doesn't the fact that Hamas and Fatha have stopped fighting among themselves, prove they are born to war?

Because Israel has begun to retaliate for the bombings from Gaza /Hamas, the Hamas and Fatha have stopped shooting at each other. It is said both of these Muslim groups will not fight among themselves, as long as Israel is bombing Gaza. WHAT kind of thinking is that!?? I guess once Israel stops the attacks, these two Muslim groups will take up arms and start waring against one another .... AGAIN!!! Are they born to kill, even if it's their own "brother"? What is your take on this?