In modern context, anyone practicing and believing in Vedant is a hindu. Geeta is in brief the whole meaning of vedas.
answer 2:
caste system is a social evil of hinduism. it has hurt the religion a great deal. just like christians have been burning witches at the altar of christ, hindus have fallen prey to this curse. But many positive things have happened. Look at UP. mayawati won beacuse of Brahmins and other upper castes.
So now I have answered yor questions, you answer mine:
1. who is lord muruggan?
2. are tamilians desecndants of ravana?
3. who is an atheist? iskarunanidhi an atheist?
4. do atheists abuse other religions?
5. if yes, then whydo dravidians not abuse an evil religion like islam, or for that matter christianity which has kiled millions in name of crusades.