Americans have no idea of what caste-based discrimination looks like and hence merely use it to foist their own prejudices (i.e. "they terk err jerbs") onto the Indian community. Indians have such diversity amongst themselves (North vs. South, State vs. State, Linguistic, Religious etc.) that anything can be used as a bone of contention (real or imagined).
The first thing to realize is that people with grievances whether factual or not, often use the American platform to push their agenda. While it makes some sense to raise Caste-based discrimination etc. within the Indian Workplace, it absolutely does not make any sense to raise it in the American Workplace simply because the repercussions would be vastly detrimental to the entire Indian Community. It is also the case that Caste-based discrimination has declined greatly in Urban India (since Independence) and more specifically in the IT sector where everybody is only after the almighty USD/INR and nothing else matters.
Hence i think Google did the right thing in cancelling this talk.