adharmābhibhavāt kṛṣṇa praduṣyanti kulastriyaḥ
strīṣu duṣṭāsu vārṣṇeya jāyate varṇasaṃkaraḥ
saṃkaro narakāyaiva kulaghnānāṃ kulasya ca
patanti pitaro hy eṣāṃ luptapiṇḍodakakriyāḥ
doṣair etaiḥ kulaghnānāṃ varṇasaṃkarakārakaiḥ
utsādyante jātidharmāḥ kuladharmāś ca śāśvatāḥ
From the predominance of sin, O Krishna, the women of that race become corrupt. And the women becoming corrupt, an intermingling of castes happeneth, O descendant of Vrishni. This intermingling of castes leadeth to hell both the destroyer of the race and the race itself. The ancestors of those fall (from heaven), their rites of pinda and water ceasing. By these sins of destroyers of races, causing intermixture of castes, the rules of caste and the eternal rites of families become extinct.
But how did Swami Vivekananda interpret these verses? Did he disagree with Arjuna and the Gītā because he thought these verses were written at a time the birth-based caste-system was the norm?
Assuming he was opposed to birth-based caste-system and still supported these Gītā verses, what does varṇasaṃkara even mean in the context of a non-birth-based caste-system?