A gene for "peace"

Where is the end? or I would like to ask when can we start a new beginning again? Mumbai massacre, more than 150 dead. It is just not an number...It is the number of families destroyed, multiples of 150 = children orphaned. What do these terrorists get by going for this killing spree? By making these families and children's life living hell, do they really go to heaven (as promised by the terrorist trainers....). Come on, can't we just live peacefully respecting the differences in religions, culture, etc. After all we have only one life.
Sometimes I get this sci-fi idea. We should artificially synthesize a gene which encodes "peace" and infect the whole mankind with this "peace" using some biological weapon. Is it possible to live and let live in harmony? Wish, it happens in my life time.....