Because the world was created to be a safe place to live in, and if everyone was created equal then we need to settle our differences like normal people instead of blowing each other up. Kennedy probably wanted peace instead of war, no one wants to fight and have to go to sleep hearing screams and bombs going off in the background, we just want to have a place to call home and a place where we know we can be safe. Either that or something was wrong with the missiles.