Commentary Purg XXVI 40

Those who have argued that the sin punished in Inferno XV and XVI is not homosexuality (see C.Inf.XV.13-21) are hard pressed to account for the obvious reference of the word 'Sodom' repeated here, used first in [Inf XI 50] to refer to the sinners on the barren sands of homosexuality.  The early commentators have no doubt whatsoever about all this.  See, for example, John of Serravalle (DDP Serravalle.Purg.XXVI.37-42): 'And from this city, Sodom, the sin against nature took its name, just as simony did from Simon [Magus].'  Each group cries out the appropriate exemplar(s) of its sin, the first the homosexuals, calling out the names of these two 'cities of the plain' (see Genesis 19:1-28), the locus classicus for homosexual lust, where the men of Sodom ask Lot to give them for their sexual pleasure the two angels who have come to Lot and whom they take for men (Genesis 19:4-11).

      What has long been problematic is the fact that, in Inferno, we find the heterosexual lustful punished in the realm of Incontinence, while those guilty of homoerotic behavior are in that of Violence (against nature, in their case).  That these two groups are now purging themselves on the same terrace may be the result of the changed ground rules for the sins of the two cantiche more than of any supposed change of heart on Dante's part, that is, Dante no longer has the option of fitting these two different bands onto an Aristotelian/Ciceronian grid, but must associate them with one of the seven capital vices, which leaves him little choice.  Nonetheless, no matter what his intentions, the effect is to make the reader feel that the poet has now softened his views.  The notion of Pertile (Pert.1993.3), p. 388, that the impulse to love is the same in hetero- and homosexuals and that, since in purgatory only the impulse (or predisposition) toward sin is purged, there is no longer any need to distinguish between them is interesting but difficult to accept.  In Inferno homosexuality is treated as a sin of hardened will, and one would be hard pressed to show that this does not make the 'impulse' that drives it different from that behind the sins of Incontinence.