How it is possible to make a candala a Vaisnava?" No, that is possible. Prabhavisnave namah. Visnu is so powerful, omnipotent. He can do that. So only by Visnu mantra, by becoming a Vaisnava, one can transcend all this restriction, sociology
-Lecture on Bhagavad-Gita 1.40 -- London, July 28, 1973

वेदाविनाशिनं नित्यं य एनमजमव्ययम् ।
कथं स पुरुषः पार्थ कं घातयति हन्ति कम् ॥ २१ ॥
O Pārtha, how can a person who knows that the soul is indestructible, eternal, unborn and immutable kill anyone or cause anyone to kill?
-BG 2.21