War in space

Perhaps there is less reason for war in space - the only reason I
could think of was location - there is no resource advantage -
everyone has to go somewhere to get basic materials - for expansion
you could build another colony - genocide would only get you
indignation of the entire system and perhaps your own demise - If you
don't like the neighbourhood then move the entire colony a few
thousand miles away- as for sending large asteroids ( large enough to
move comfortablely ) perhaps a recieving habitat would welcome them
with a fleet of scavange craft that would take them in pieces and use
the materials in the colony. It is possible that a blockade would work
really well though and you could force a colony to deplete its
resources in maintaining itself and thereby surrender to you.