How does one then converse with a person who doesn't understand his/her tongue ? and what if it is to be a conversation between an arab and an asian , either one of them not knowing english? In which case english as an option should be ruled out(perhaps it can still exist as an option,provided speaking 'broken' english does not spark another controversy).
Summary-mother tongue as the first choice is ruled out and if the person does not know english,the second option is ruled out as well.In such a scenario a person is left with no choice but to simulate a deaf and mute conversation.