To say that life only matters because it is short is akin to saying that cake for dessert only matters because you had feces for breakfast. We've discussed the law of contrasts before in Torture, Murder, and Pain Prove You Exist and An Idealized Reality. Let us consider the comment again in light of the common Terran argument that only imperfection can make perfection possible. You may have experienced some of these philosophical poisons before. Contemplate:
"We can only recognize beauty because everything isn't beautiful. If everything were beautiful, we would have no standard by which to judge beauty; therefore, beauty would not exist."
"Life only has value because we are mortal. If we lived forever, nothing would matter."
"God has a plan. His reality only appears imperfect because the free will given to unrepentant sinners whom He knew would sin and not repent makes the beauty of others' repentance more profound."
These all are, in essence, the "cake only tastes good if you know shit doesn't" argument. They are absurd, and absurdly wrong, however, their true strength lies in the subtle conflation of the moral extremes which they present as false opposites. If, for example, fresh chocolate cake could not taste good without the ability to compare the experience of eating it to the experience of eating feces--or, if you prefer, the experience of eating instant oatmeal--then eating feces is good, because it is the foundation upon which cake itself rests. Conversely, under the rubric of the positive mortality argument, massacring preschoolers is good, because it adds value to the lives of the survivors (or of the sheltered unaware set of hypothetical preschoolers) by vindicating the comparatively superior survivor experience. We see this play out in the news, where hypothetical contrasts (whether they physically occur as described or not is irrelevant) permit us to define our own experience as positive or negative, or to identify with a group, experience empathy, et cetera, therefore strengthening our existential quandary--not through anything we do or witness, but through sheer speculation.
The Jewish-Christian Satan makes this argument too, becoming thereby the hero of the false dichotomy between benevolent-creator and malevolent-creator incurred through the corruption of Gospel with Torah. Satan, by sinning and enticing others to sin, permits goodness itself to exist, in a way that God never can. The wretchedness of the Jewish-Christian hybrid religion--a product of planned obsolescence, designed not merely to fail, but to fail in embarrassing and deleterious ways--is most fundamentally expressed in the necessity of evil to define good in this broken world. Due to the flaws in the material world, materialism, and thereby the cursed creator himself, must win the long argument; the Overton Window of Torah-based Christianity means that goodness is a zero-sum game, ergo the edited Gospels' keen interest in the legalistic stipulations of sin- and forgiveness-based negotiation. The Jewish-Christian God has necessarily to be a cuckold and a Flanders, hyper-unrealistically flawed, in order to spend his time in the pillory making Satan's rebellion suitably heroic.
The Law of Contrasts is false, in its own way, and it is a comparatively elementary matter to demonstrate that falsity, as when an omniscient and omnipotent devil giving an infant terminal leukemia is of less concern than a father of three glancing through a dirty magazine. Yet despite its falsity, it is necessary for some--those not bright enough to move beyond it do need to eat a little shit before they can eat a little cake, and would not understand beauty without first witnessing the hideous. It is an intellectual privilege of sorts--a "let the baby have his bottle" moment--to not require the primal validation of opposites in order to experience anything, and it is correspondingly selfish and immature to not, in a rather libertarian fashion, permit others the occasional reverence for the simple tools they require in order to be able to understand that they exist, and to make sense of the sensations they experience using the only way they know how.