Kevin Ray does a great job of diagnosing the problem with the Pope's view:
the view the Pope adheres to in these statements diminishes humanity, the family and marriage -- reducing all to mere biology, where marriage and family are naked husbandry and human nature is bestial at best. A less spiritual view of human nature and man's place in the world is difficult to conceive. If the Church is to remain true to its traditional view that individuals (including gay individuals) mirror the nature of God, this impoverished representation of man's nature must be rejected.
Moreover, this perversely narrow view of man's fulfillment in the world has consequences beyond a profound misunderstanding of homosexuality. This same narrow view that man's only purpose is "begatting" leads to a reckless absolute prohibition of birth control, with worldwide overpopulation and poverty as a result. This same medieval thinking precludes sane and effective methods for preventing the spread of disease. (Some within the church hierarchy have attempted to have a sane conversation about condoms and disease prevention, but have been sternly slapped down by the conservative defenders of doctrine.) To paraphrase the pontiff, I would suggest that it would be legitimate and necessary for the Pope to ask himself if this is not perhaps part of an old ideology of evil, of the most insidious kind (misguided benevolence), which attempts to pit an irrational dogma against the family and against man.