Is the Hinduism v/s Islam fight new or has been going on for generations? Is there a mention of Islam in ancient Hindu texts like the Vedas?
Hindu scriptures long predate the rise of Islam. I would say that Hindu-Muslim relationship has been bad for many centuries. The 1202 storm campaign of Muhammad Ghori resulted in the destruction of hundreds of Hindu temples. There is no doubt ( in spite of the efforts of secular historians) that Nalanda was destroyed by the Muslim invaders. The common Hindus were forced to pay Jizya tax.
According to some estimates Muslims killed 80 million Hindus in their long 600 year rule. Their rule can be summed up by this quote:
"If the revenue collector spits into a Hindu's mouth, the Hindu must open his mouth without hesitation" -- Qazi Mughisuddin legal officer of Sultan Alauddin Khilji
(REF:ELLIOT and DOWSON, The History of India, as Told by Its Own Historians; The Muhammadan Period ( 1876-77)).
There was also forced conversions of Hindus by Muslims. An infamous example of a forcible conversion attempt was Aurangzeb's attempt to convert Kashmiri Pundits to Islam in the 1670s. Kashmiri Pundits were saved by the Sikh Guru Tegh Bahadur who was executed by Aurangzeb for defending the rights of non-Muslims to live in India.
Another example would be 16th century Varanasi. Muslim clergy made it impossible for Hindus to live peacefully in Varanasi. Sri Madhusudan Saraswati met Akbar and told him of the plight of Hindus. Akbar told him that he should form his own forces to resist the Muslim clergy. It is Akbar's advice that led to the birth of Naga Sannyasis.
Will Durant, the famous historian summed it up like this:
"The Islamic conquest of India is probably the bloodiest story in history. It is a discouraging tale, for its evident moral is that civilization is a precious good, whose delicate complex of order and freedom, culture and peace, can at any moment be overthrown by barbarians invading from without or multiplying within."
The Story of civilization by Will Durant
Any other civilization would have been destroyed if they had suffered 80 million casualties. This long unfortunate 600 year old history of Muslim rule throws a long shadow even today.
The present day reality is also unpleasant. Hindu population in Pakistan has declined from 15 % in 1947 to probably about 2 % today while Muslim population of India has increased from 9 % in 1947 to 14 % today thus giving rise to fears. Kashmir valley has seen cleansing of 500,000 Hindus in the 1990s.
The Vedas are from about 1500 to 500 BCE. Islam is from the 7th century CE. Hence there is no mention of Islam in the Vedas.
However, it is known from internal evidence that the Vedic texts were orally composed in northern India, at first in the Greater Punjab and later also in more eastern areas, including northern Bihar, between ca. 1500 BCE. and 400 BCE.
Michael Witzel: Vedas and Upanisads in Flood, Gavin (Ed.): The Blackwell Companion to Hinduism (2005).
Hindu scholars somtetimes give much older dates for the Vedas, e.g.,
Dasgupta, Surendranath: A History of Indian Philosophy. Vol.1 1922.
He quotes Max Mueller ca. 1.200 BCE., Haug 2.400 BCE., Bal Gangadhar Tilak 4.000 BCE.
Speaking of absolute mention of Islam in Hindu texts: there is no such thing.
However, speaking of the concepts, it is clear that any Advaita scholar will be totally in phase with any Non-dualist Muslim. Ramakrishna and René Guénon proved it. Ramakrishna was a Hindu who validated Islam. René Guénon was a Muslim who validated and taught Hinduism even more than he taught Islam in Europe.
The problem is always with the people that misunderstood that there can not be one way to fit every single human. These people won't even accept nuances between people of the same religion, how could you expect them to accept other religions?
They are the test for non-dualists and this has to be accepted as a matter of fact.