Does the idea of white Europeans being the “true Aryans” come from the British India?
No. According to some sources the idea originated in Germany
[...] it was the word early 19c. European philologists (Friedrich Schlegel, 1819, who linked it with German Ehre "honor") applied to the ancient people we now call Indo-Europeans, suspecting that this is what they called themselves. This use is attested in English from 1851. In German from 1845 it was specifically contrasted to Semitic (Lassen).
German philologist Max Müller (1823-1900) popularized Aryan in his writings on comparative linguistics, [...]
The Encyclopedia Brittanica says
In Europe the notion of white racial superiority emerged in the 1850s, propagated most assiduously by the comte de Gobineau and later by his disciple Houston Stewart Chamberlain, who first used the term “Aryan” to mean the “white race.” Members of that so-called race spoke Indo-European languages, were credited with all the progress that benefited humanity, and were purported to be superior to “Semites,” “yellows,” and “blacks.” Believers in Aryanism came to regard the Nordic and Germanic peoples as the purest members of the “race.” That notion, which had been repudiated by anthropologists by the second quarter of the 20th century, was seized upon by Adolf Hitler and the Nazis and was made the basis of the German government policy of exterminating Jews, Roma (Gypsies), and other “non-Aryans.”
The comte de Gobineau was French. Houston Stewart Chamberlain was a British-born German philosopher.
Chamberlain's best known book is the two-volume Die Grundlagen des neunzehnten Jahrhunderts (The Foundations of the Nineteenth Century), published in 1899, which became highly influential in the pan-Germanic Völkisch movements of the early 20th century and later influenced the antisemitism of Nazi racial policy.
It describes how Chamberlain was unhappy with his life in Britain and moved to mainland Europe where his political outlook changed and he became an influential proponent of views associated with white Aryanism.
So the idea of white Europeans being the true Aryans arose primarily outside Britain and not from British India.
"Aryan" as justification for Colonialism
The word Aryan has its origins in Sanskrit and, in 19th century Europe was associated with the invasion of India by Sanskrit speaking people.
a man from India [...] said [...] This helped [the British] to justify colonization
Not in the first 200 years of European and British colonialism in India. The dates don't support this.
- British colonial involvement in India began long before the development in Europe of the ideas of Aryanism described above.
- British colonialism began long before the involvement of the British in India.
Wikipedia gives these dates for Colonial India:
|Casa da Índia
|Portuguese East India Company
|East India Company
|Company rule in India
So the notions of Aryanism from 1819 occur long after the onset of colonialism in India.
Some say Ireland was Britain's first colony, and that was begun in the late 1170's by French-speaking Anglo-Normans who were descendents of the Normans who had invaded and conquered most of Britain.
So colonialism was an established idea long before British involvement in India. Colonialism in general didn't rely on any ideas about Aryianism because it predated them.
There's little doubt that ideas of European supremacy were a part of at least later European post-hoc justification for European colonialism but trade and mercantilism were probably the primary driving forces in the early colonial era.