Riddle,
Are you trying to make a riddle out of it? Why do you think he should not speak english, if he does not have clear grasp of it? So lets see this: Origin of English is England, and a English man ask you some question in a Cockney accent, and while you think you know english enough to answer the question, you do not know typical word he is using. and you ask him what does it mean? and that guy starts laughing at you, and somehow you feel nervous about it and can not answer the question. So Conclusion made by you would be you should not use english at all, no? You should answer him in Nepali, no? or some jibber jabber, no? 
Well, it is just my opinion, and as they say Opinions are like an asshole, everyone has one.