response from QLers'

Instead seeking our opinion, clearly referring to a nationality is NOT a correct approach..

To be more professionally, he should have discussed with his colleagues to ensure 'use of common language' in the office especially when in presence of clients.

We all know regarding effective communication and office ethics :)

it is a general trend with all languages......similarly I have seen South African, Sri Lankans, Arabs, Keralites, Mangalorians, many more, who feels more comfortable while discussing in their own languages.

From disciplinary PoV; it is NOT courteous to speak in any foreign language when in a group and well aware that few would not understand, one could avoid vernacular language.