Sangram was telling me the other day how odd it was to hear one of his Indian collaborators say,'Forget about it!' in response to his,'Sorry about that!'Though it is quite the standard response in Indian English to an apology, we are now more tuned to hearing,'Oh that's okay!' or 'Don't worry about it.' Just as 'Be quiet' is a more polite way to say, 'Shut up!'
I used to say 'Chill Yaar!' a lot in college. In fact, I think I once said it to my Dad, and he responded, 'Nahi Yaar!' Not everyone is a sport about it. Someone I know was unfriended on Facebook (and in real life) because she responded,'Chill !' to a comment. At that time, I didn't realize that it can sound rude in certain contexts.
Language is a living, dynamic thing. Our usage and preferences also change over time with the environment. If someone speaks loudly, I feel why he/she is so rude? When most of the times, they are just animated. Maybe if we are aware of the nuances, we can avoid miscommunication in different cultural contexts.