Wicked Wanda,

I think that the claim that homosexuality is a sin does indeed originate in Pauline theology, specifically his letter to the Romans, verses 26–28, and 32.

That the Catholic Church does, on occasion, have a more relaxed attitude towards homosexual lifestyles than some of the more entertaining Protestant sects do is, I suggest, due to a developed tolerance of the wide range of lifestyles it has had to accommodate over its 1,700 years or so of continuous operation.

This tolerance itself has, if I remember correctly, also been the source of occasional difficulties and controversies.

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Eudaimonia