Why society is still not ready to accept intercast mariage specialy in UP and Bihar,any way to chnge d society?

Hi I am 23 yrs old.I love a girl and want to marry with her but the problem is my parents are not ready for the same because she is from a low caste though they know she is a nice girland i know they would have accepted her if she would have been from the same caste .My parents say only cast is the problem, no one accept it in society our family's honour and pride would be spoilt...I have two younger sister and parents say my this act would creat problem in their marriage as well( I also know this )..so now I have been given two options either leave that girl or leave them(Parents) ......but I dont want to leave any one of those bcz if i leave any one of them i cant live....what should be done ...plz help me .....if any suggested act which could open the eyes of my parents would be highly appriciated .....bcz I not only want to marry with this girl but also want her to be accepted by my parents as well with dignity....plz help me...FYI ,,,I am finanacially selfdependent ...