Hey Mike,
Having sins ranked is a general and well-established norm among Catholic moral theologians, particularly the original Scholastics (later Scholastics admittedly got a bit absurd though).
You can find the rankings variously distributed throughout Thomas' Summa Theologiae, for example. He reasons that because the two ends of marriage are unitive and procreative, the sexual sins that most frustrate those ends are the most sinful because they violate what God intended for human sexuality. inappropriate behavior with animals is clearly the worst since it not only is non-procreative, it's not even within our species, and hence has absolutely zero unitive power.
See especially
this Article from Thomas:
On the contrary, Augustine says (De adult. conjug. [The quotation is from Cap. Adulterii xxxii, qu. 7. Cf. Augustine, De Bono Conjugali, viii.]) that "of all these," namely the sins belonging to lust, "that which is against nature is the worst."
I answer that, In every genus, worst of all is the corruption of the principle on which the rest depend. Now the principles of reason are those things that are according to nature, because reason presupposes things as determined by nature, before disposing of other things according as it is fitting. This may be observed both in speculative and in practical matters. Wherefore just as in speculative matters the most grievous and shameful error is that which is about things the knowledge of which is naturally bestowed on man, so in matters of action it is most grave and shameful to act against things as determined by nature. Therefore, since by the unnatural vices man transgresses that which has been determined by nature with regard to the use of venereal actions, it follows that in this matter this sin is gravest of all. After it comes incest, which, as stated above (Article 9), is contrary to the natural respect which we owe persons related to us.
Thomas is hard to understand in this unless you understand what he established earlier in his Summa, but there are other writers today who put it in easier terms. Thomas doesn't mention inappropriate behavior with animals but it is broadly agreed as being the gravest sexual sin one can commit, then homosexuality, and then (as Thomas says) incest.
The sexual sin that is traditionally considered least grave is fornication, if I'm not mistaken.
To Benedicta, the Blessed One,
but hell is hell right?
My deal is not saying this sin is no big deal but that we are worried about it while we act like the sins that are rampart are not a big deal becuase its not as bad.
If people are going to hell, then they are going to hell, be it a gay or a straight.
I'm just not getting what it matters if its worse.
It does matter for several reasons. First, different sins have different effects upon the spiritual life and on the spiritual well-being of the one who commits them. Lust is well known among Mystical Theologians as causing a particular hatred of God and of Religion, and blindness of the soul. The deeper and more grave that sin becomes, the more and more blind one becomes to spiritual realities. This is also generally true of Pride, but Pride does not cause the same type of blindness.
Furthermore, in this case, if the vice of lust becomes so culturally pervasive that we can no longer depend upon general society to aid us in being virtuous, we will find that it will lead to a collapse to a general sense of moral norms and what our Holy Father has called the "eclipse of God" in Madrid this week. Also, the all vices surrounding lust are so common (because of our fallen nature) that they tend to have a ripple effect throughout a society and also within the heart. Pride, avarice and sloth generally tend to be solitary sins. Lust often is not, except for the one.
The greater the sexual sin, (all sin, actually, but most especially those of lust and pride) the greater the darkness becomes and the more difficult it is to penetrate.
This all being said, I 100% agree with you, Benedicta: sin is sin, and its gravity is what it is, regardless if one person does it or one million. However, certain sins are more grave than others and do demand greater attention, both pastorally and in our prayers and loving outreach.
