Our goal should be to fill the universe and make it dance with as much life and consciousness as possible. Of course we should be cautious not to ever loose or destroy any potentially existing life. But we believe all life wants to grow, expand, and become social, and that we should assist with all possible "uplifting" efforts all according to their will.
But we must be cautious about what life we spread. If we fill a planet with wildlife similar to earth's, then we are morally responsible for all of the suffering experienced by all life on that planet. There is also the possibility that lifeforms on this planet will evolve into something hostile, that will try to attack other planets.
We don't want to just spread life for the sake of spreading life. We want to fill the universe with beings living happy and fulfilling lives.