I think, as Pertinax has alluded to, that there is a difference according to how long the word has been part of the English language. Words that have been around for longer are more likely to be seen as "English" words and accorded their own "correct" English pronunciation, whereas more recent borrowings are likely to be seen as "foreign" words and people are more likely to try to reproduce the pronunciation of their language of origin. (Of course, this is not a hard and fast rule, some words just seem to integrate more readily than others.)
This is only speculation on my part, but I also have a theory that we privilege some languages of origin over others. It seems to me that mispronouncing French (or unassimilated French loan-words) has long been stigmatised, whereas we have collectively only started caring as much about how we pronounce words borrowed from other languages relatively recently. For example, I seem to hear more people (in a European context) attempting to pronounce things like 'Valencia' or 'risotto' in a (respectively) Spanish or Italian manner more often now that I think would have once been the case, whereas I think pronouncing things like 'Quimper' or 'crème brûlée' in a French manner has long been a sign of being well-educated. I imagine this is due to a shift in which foreign languages are seen as prestigious to learn or are widely spoken in English-speaking countries and also due to broader cultural changes (for example, changes in what sorts of food people are eating or which travel destinations are popular). Perhaps in the future we'll see more efforts to pronounce, say, Chinese or Hindi loan-words, foods, etc. "correctly" more often than we do now.
(I hope my response is sufficiently on-topic to the original question.)