To compare millions getting killed through centuries of almost
constant warfare and chaos, with millions getting killed through
willful policy of mass-murder is not fair, to sayt he least.
The fact is, millions of Chinese, as well of west-, Central Asian
muslims lost their lives during the Mongol invasions and wars
of the 13-14th centuries, but I wouldn't compare that in "nature"
to the WWII Holocaust. Probably even more than those of India
in those five centuries, and here in only less than half the time.
The Middle Ages, like Ancient Times, and indeed much of human
history, was filled with constant warfare and violence, where more
often than not human life was worth little to rulers and soldiers
(much like today, though today the civilian populations,
especially in the West, is less tolerant of their leaders commiting
mass atrocities).
A better comparison with the WWII Holocaust, would be the
Armenian Genocide, or Rwanda, or the mass killing of the North
American Indians.
That site was just sectarian propoganda. Probably run by one
of those extremist Hindu "nationalists" who hate Muslims,
Christians, and Buddhists with equal fervor.