I'd read the above as: "I have a demand, I feel that it is perfectly normal to request things in this manner".
This suggests a knowledge of the difference between the two words. Hence, he is not ignorant of the difference. It is his choice to use the word 'demand' and the intonation thereof - so why should we treat him as an imbecile with no knowledge of the English language purely on your say-so? I'd say he has demonstrated a decent grip on the language and intonation to be frank, and as such I have no intention to treat him as if he does not.
Apologies for having a good upbringing, and sorry my parents worked bloody to give me it when I was a kid. I'll be doing the same for my children - giving them the best chance in life I can - feel free to not do the same for yours due to some anti-elitist pretence or some such.