Admixture of varṇas conduces to hell for the lineage as well as the destroyers of lineage. The ancestors will then fall from their lofty domain, due to lack of the customary ‘rice-ball offering’ and allied rituals performed for the sake of departed souls.
Every kshatriya male is expected to conduct rituals to benefit the departed souls of his lineage. For this, he must have the requisite social status. Inter-caste alliances destroy the family as well as the traditional rituals, leading them to the worst of hells, wherefrom there is no escape.
For, those born of inter-caste alliances lose their right to perform the traditional rituals. They would not have any inclination either in this regard. The usual hereditary training missing, the opportunity to learn is also not there.
Denied the grace of yearly and occasional ritualistic offerings, the departed souls fall from the higher abodes, where they have been for long. All these thoughts and considerations make Arjuna weak and restless.