Secret languages
I often go to the Subway up the street to eat lunch. Most of the
employees there are Indian women that appear to be native Urdu
speakers. They all speak pretty good English, but most of the time
they talk to each other in Urdu, even while they're serving
customers.

I have a rudimentary understanding of Urdu--not good enough to
speak, but good enough to get the basic gist of a conversation going
on around me. Most of the time they chat about mundane things, but
every now and then they talk about the customers they're serving,
and typically in unfriendly ways. I get that it's more comfortable
for them to communicate with each other in their mother tongue, but
I find this behaviour, even without the unfriendly comments, to be
very rude. It probably doesn't help that they don't do any of the
social things I associate with being friendly, like smile or make
eye contact.

Am I being too harsh? Should people working with the public speak
whatever language they want with their colleagues? Does it matter
what the content of the conversations are?