And (related to the viewpoint ImreSkip already put forth):

When the rest of us die in peace, knowing our distant descendants will roam the spiral arms and rule the galaxies, we'll take great pleasure -- enabling us to go forth on that last journey with a smile on our lips -- in knowing that Marlowe's descendants (if he has any -- what sane woman would want to mate with such a stain on mankind's reputation?!?) WILL HAVE TO STAY HERE AND ROT, AS PUNISHMENT FOR GRANDPA PHIL WANTING TO DOOM THE WHOLE SPECIES TO DO SO!

Such genetic material is obviously not fit to travel in (and conquer) space, so it's only for their own good... At least that's what we'll tell them. And, hey, Marlowe can't hardly disagree, now can he?