I can’t seem to quote the CDF bit from fix’s post, but I can copy and paste it:
To chose someone of the same sex for one’s sexual activity is to annul the rich symbolism and meaning, not to mention the goals, of the Creator’s sexual design.
We are assuming, at least for the sake of the discussion, that the selection of a same-sex partner is not an arbitrary choice, but the result of a deep-seated sexual orientation. If I ever get married, it won’t be because I drew lots and they indicated that I should seek female company; it will ultimately be because I am, irreversibly and involuntarily, a heterosexual male. I am attracted to muliebrity, not virility. Similarly, if a woman seeks a woman, it’s most likely because she is, irreversibly and involuntarily, a homosexual female, and just as much attracted to femininity rather than masculinity.
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Homosexual activity is not a complementary union, able to transmit life; and so it thwarts the call to a life of that form of self-giving which the Gospel says is the essence of Christian living.
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This appears to imply that complementarity is a matter of being able to procreate, but this could be easily handled if the sterility analogy holds up (again, that’s a big “if”).
This does not mean that homosexual persons are not often generous and giving of themselves; but when they engage in homosexual activity they confirm within themselves a disordered sexual inclination which is essentially self-indulgent…
Of course there are plenty of lustful homosexuals with no interest in monogamy, commitment, or anything else that isn’t immediately gratifying. But there are plenty who are interested in something less selfish. I can’t see how the latter are being self-indulgent.