Cardinal Biffi notes that the “homosexual ideology” fits right into the present context of pan-sexuality, an idolatry of sex ‘liberated’ from any objective moral norm. It is at the same time a symptom and a consequence of both the abandonment of God and the theoretical and practical atheism of our times.
According to Saint Paul, aberrant practices are a punishment for that abandonment, which leads people to a kind of mental imbalance: "They became vain in their reasoning, and their senseless minds were darkened. While claiming to be wise, they became fools."
This type of madness causes a degradation of the body as well:
"Therefore, God handed them over to impurity through the lusts of their hearts for the mutual degradation of their bodies."
Man thus becomes dominated by the most violent and degrading passions:
"Therefore, God handed them over to degrading passions. Their females exchanged natural relations for unnatural, and the males likewise gave up natural relations with females and burned with lust for one another. Males did shameful things with males and thus received in their own persons the due penalty for their perversity. And since they did not see fit to acknowledge God, God handed them over to their undiscerning mind to do what is improper."
Acceptance of vice eventually leads man to try to justify it from a doctrinal standpoint, thus creating an ideology. Hence Saint Paul concludes his analysis: "They [who practice such things] not only do them but give approval to those who practice them."
Read it all here.