India doesn't share DNA data with Reich's lab, and Harvard's data is fairly small (though being from the West, they can make bombastic claims about "aryans bringing civilization" etc.).

The Indian scientists who work on this (Niraj Rai / Shinde), who have co-authored with him, and have access to a lot more data, strongly disagree with his views.

Archaeologists have for 30+ years noted that there is zero-evidence for mass-migration. Evidence in Linguistics is barely acceptable, and even there its clear that it is forced.

European/Western nationalism is strongly at play here - though as with everything since its "normalized", people don't even think it's wrong or despicable. They just happen think anyone opposed to the "chosen people" are scum of earth (surprise surprise).