I wish to know why some Indians show racism against the others...... :(?

There is no one answer for you questions. There are lot of reasons....BUT one common is thats how we raised in India....its just not that you from south and they are from marathi...even in Marathi they have different cast and all .....so peace and just learn to ignore and be tolerant. I found americans are the least racist...we just hype a lot...You will see racist in every culture so its nothing new.....Dont' blame them...it just how they raised....