I understand your points but it is often very much the way it is said...in a very patronising and British Empire style way. (Don't get me started on the BE, who went into many countries and adjusted the country to fit themselves, not the other way around). A 'duty to assimilate'? Are immigrants Borg? (Star Trek reference) Immigration does indeed need to be treated really carefully but also with some sensitivity. Many people - British in particular - go to countries and do not bother to speak the language. They stick to little ex-pat enclaves. What is the difference?
That said, I feel it is helpful to feel less lost, as a foreigner (my family are from India) to be able to understand and relate.
So to speak of it being a 'duty' is unhelpful. To say that it would be great if we could also discuss the issues, would be better.
I witnessed a friend of a friend speaking in a a violent and hate-filled way (she spat) about the 'poles coming over here....' Her family came over from Ireland in a time when they were considered a plague and hideous notices were put up: 'No blacks, no dogs, no Irish.' They were once the hated immigrants. They forget.
Also few people resent the slavic or australian influx...and there are quite a number...so often it does pin down to colour and sadly, pure racism.
So yes, there needs to be dialogue but 'these immigrants' (horrible phraseology in itself) do not need to be talked down to in a high-handed British Empire style. Why not criticiss the ex-pats in Spain who barely speak a word of Spanish.
No, I do not consider any country is 'your' country because you live there, speak the language etc. The world is in flux and will increasingly be so.