[vegabook]

> The key, and I think this applies to any language, is not NOT BACK DOWN. Some things will be hugely painful, if you back down you just defer the pain [...] don't let them

This is very stressful. Forcing an interlocutor to speak to you in their tongue when they know your language much better than you know theirs, is basically rude, and persistence with impoliteness is stress inducing for many people. I have personal experience of this in France where people would insist on speaking to me, stutteringly, in my native English when I speak perfect, fluent, French. Thus the OPs point about the language barrier being an issue, IMO is very valid.