Just because Chandalas are born from Sudra Father and Bramha mother,How justified is it to outcaste them and allocate menial and disgusting jobs?? Could they change their occupations if they gave up meat eating and cruel habits??
No it is not justified. Nor is the definition of Chandala being born of a Sudra father and a Brahmana mother correct. These fanciful Smriti concepts are clearly wrong and are against the Vedas. This is clear from the Chandogya Upanishad definition of Chandala.
Those whose conduct here has been good will quickly attain a good birth (literally womb), the birth of a brahmin, the birth of a Ksatriya or the birth of a Vaisya. But those whose conduct here has been evil, will quickly attain an evil birth, the birth of a dog, the birth of a hog or the birth of a chandala.
Chandogya Upanishad V.10.7
As you can see Chandogya Upanishad is specifying conduct as the reason for different births. It has nothing to do with the caste of the father or the mother.
What does the Chandogya Upanishad verse mean?
It has nothing to do with the caste system invented by the Smriti writers. It means that depending on the amount of good conduct a person will be born to parents of high Sattva Guna (Brahmin), to parents of middling Sattva Guna (Ksatriya) or parents of high Rajasa Guna mixed with some Sattva Guna (Vaisya). The vast majority of persons with neither good nor bad conduct will be born of parents who do not have the gunas of Brahmanas or Ksatriyas or Vaisyas but whose conduct is not as bad as that of animals.
Those whose conduct has been exceptionally bad without any redeeming feature will have animal parents or human Chandala parents. This suggests that Chandala is defined as a person whose conduct is like an animal.
Example of Chandalas
The Nazis who gassed Jews were Chandalas and will have either animal birth or parents of the Chandala type.