Caste

I am so saddened to see our Hindus discriminating against each other in the caste system. When comes to marriage they are practicing the caste system which never exists in our dharma. Whose fault is this? Why do we have to follow this till today and teach our children about it? Whereas in the top most holy book Bhagavad Gita, it is written "panditah sama-darsinah 5.18". One should see every living entity equal vision a learned and gentle brahmana, a cow, an elephant, a dog, and a dog-eater. Even after the topmost instruction, we are still disobeying the Lord's instruction. Can we be a Hindu or Sanatana Dharma practitioner when we disobey the instruction of the Lord? Please discuss and Let me know what your opinions.