In reaction to the majority of the conversation below being centered around the swift implementation of stern retaliation, if I were at the table of this conversation, I would introduce the following idea to the multiifaceted conversation. Not to be confused with the right way but an additional one.
What was said? Why is that not part of the conversation we are having?
Cultures meeting takes time. Think world history.
Resist the urge to fight fire with fire. Cook meals on them or put them out.
Who's to say that these derogatory comments were not actually based on a documentary is about India that only highlighted the bad parts? Or who's to say that these peoples limited interactions were simply poor so far. A stern talking to is in order but not without further conversation about WHAT was said and WHY. Let these individuals walk away with a positive, personal interaction not a story about being caught.
Fix your PR problem by using this as an opportunity to put that person on the plane to India for the same price that it would cost for you to fire them and re-train someone else.
I would say in general, in America, Indian culture here is just catching on and it's going to take the persistant exploration of people's comments, and pulling them apart and not saying "all racial comments or bad or wrong" or "any comment that hurts anyone is wrong or bad" but what if we said: Can we talk about it?
Call the manager. We don't know enough about the situation to assume that those people are hateful. So far, just ignorant!
PS I am Ankit's classmate and he asked for my opinion.