On the subject of whether “-ese” is offensive, are people from Vienna offended when they are called “Viennese”? I am part Portuguese. Should I be offended? What about Milanese? Piedmontese? Maltese?
All of the above have to do with places in Europe. “-ese” is most certainly not a derogatory ending for Asian people. Not to mention Congolese, Senegalese, Sudanese, Surinamese, etc. Also note: Korean, Mongolian, Thai, Malaysian, Cambodian, Laotian, Singaporean; all having to do with eastern Asia, but do not have the “-ese” ending.
It comes from the Latin ending “-ensis”, and its equivalents are seen in Spanish “-es”, French “-ais” and “-ois”, and Italian “-ese”. Digging farther back into Indo-European roots, it’s related to English “-ish”, German “-isch”, Scandinavian “-sk” and Russian “-ski”.