Hindus could tolerate low castes very well - that is why almost 50% of kings of princely states at the time of independence were Shudras!
There are castes among Indian Muslims too - Ashrafs being superior to the Ajlafs.
No matter what the internal differences among Hindus are, they are not instructed by their religious scriptures to kill for unbelief or belief in the wrong religion.
After Muslim rule of 1000 years, we got Pakistan and Bangladesh - standing tributes to Islamic tolerance!
