Objection 1. It would seem that intemperance is not the most disgraceful of sins. As honor is due to virtue so is disgrace due to sin. Now some sins are more grievous than intemperance: for instance murder, blasphemy, and the like. Therefore intemperance is not the most disgraceful of sins.
Objection 2. Further, those sins which are the more common are seemingly less disgraceful, since men are less ashamed of them. Now sins of intemperance are most common, because they are about things connected with the common use of human life, and in which many happen to sin. Therefore sins of intemperance do not seem to be most disgraceful.
Objection 3. Further, the Philosopher says (Ethic. vii, 6) temperance and intemperance are about human desires and pleasures. Now certain desires and pleasures are more shameful than human desires and pleasures; such are brutal pleasures and those caused by disease as the Philosopher states (Ethic. vii, 5). Therefore intemperance is not the most disgraceful of sins.
On the contrary, The Philosopher says (Ethic. iii, 10) that "intemperance is justly more deserving of reproach than other vices."
I answer that, Disgrace is seemingly opposed to honor and glory. Now honor is due to excellence, as stated above (Question 103, Article 1), and glory denotes clarity (103, 1, ad 3). Accordingly intemperance is most disgraceful for two reasons. First, because it is most repugnant to human excellence, since it is about pleasures common to us and the lower animals, as stated above (141, 2,3). Wherefore it is written (Psalm 48:21): "Man, when he was in honor, did not understand: he hath been compared to senseless beasts, and made like to them." Secondly, because it is most repugnant to man's clarity or beauty; inasmuch as the pleasures which are the matter of intemperance dim the light of reason from which all the clarity and beauty of virtue arises: wherefore these pleasures are described as being most slavish.
Reply to Objection 1. As Gregory says [Moral. xxxiii. 12, "the sins of the flesh," which are comprised under the head of intemperance, although less culpable, are more disgraceful. The reason is that culpability is measured by inordinateness in respect of the end, while disgrace regards shamefulness, which depends chiefly on the unbecomingness of the sin in respect of the sinner.
Reply to Objection 2. The commonness of a sin diminishes the shamefulness and disgrace of a sin in the opinion of men, but not as regards the nature of the vices themselves.
Reply to Objection 3. When we say that intemperance is most disgraceful, we mean in comparison with human vices, those, namely, that are connected with human passions which to a certain extent are in conformity with human nature. But those vices which exceed the mode of human nature are still more disgraceful. Nevertheless such vices are apparently reducible to the genus of intemperance, by way of excess: for instance, if a man delight in eating human flesh, or in committing the unnatural vice.
Source: Summa Theologica (New Advent)