This person is spreading propaganda.

Read Manu Smriti, Yajnabalka Smriti, or Parashara Smriti.

You can find them online.

In Bhagavad Gita, there are no verses that directly say bad things about so-called lower castes, but liberation is offered to people "even if" the seeker is a woman, a son of a prostitute, or a "dog-eating lower caste".

The Hindu scriptures themselves are casteist and sexist.