Prejudice against pidgins or mixed languages is deeply rooted among scholars, even linguists that should know better. Here is the beginning of the article "Altaic Influences on Beijing Dialect: The Manchu Case" (1996), by Stephen A. Wadley:
"Going even further with respect to the situation in northern China, [Mantaro Hashimoto] theorized that during the Qing (Manchu) dynasty (1644-1911), the language of the capital was not Chinese but rather a pidgin made up of Manchu and Chinese elements, as well as a few elements from Mongolian and other minor languages. Furthermore, he suggested that modern Beijing dialect was a descendant of that pidgin. Though this theory is impressionistically persuasive, the major obstacle in accepting it is the lack of solid empirical evidence. It might be expected that little or nothing would be written in this hypothesized 'mixed' language. Pidgins rarely, if ever, produce a literature. Hashimoto pointed to several texts of zidi shu (a type of 'drum song' popular in northern China during the Qing dynasty that were written in a mixture of Manchu and Chinese as a proof that the mixed language he hypothesized actually existed. Charles Li has argued convincingly that these texts were purposeful manipulations of the two languages, much in the same way that macaronic verse in the West was often simply a manipulation of Latin and a vernacular language to produce a comic idiom for the enjoyment of those who had to study Latin. Indeed, it would be unusual for a pidgin to assume the form of the language in zidi shu, since most pidgins rely on essentially a single language for their lexicon, rather than being a mixture of lexical elements. The fact that there are so few texts in this form also argues against them being a representation of the spoken language of time - although more and more texts of this type are coming to light.
"The evidence given us by the existence of zidi shu should not be abandoned entirely, however. The fact that the texts were produced tells us something about the language situation in northern China. First, there must have been some, even much, bilingualism among the inhabitants of Beijing then, otherwise there would be no audience for the pieces. Ji Yonghai has in fact presented evidence that the Manchus went through a period of bilingualism before abandoning their language for Chinese. Second, although the mixed-language zidi shu appear to be deliberate manipulations of language for comic effect, one may assume that part of the comedy is that the language parodies an actual language situation. As Whinnom has pointed out, target-language speakers often parody the language of non-native speakers of the language, not in the way they actually speak, but rather how they are perceived to speak. Thus they may produce evidence of a mixed language even though they do not produce the actual mixed language. In the zidi shu text Chaguan ('Inspecting the Pass') the Manchu language is put in the mouth of the chou (clown)."
Perhaps the prejudice stems not just from sociological causes, but from literary theory itself. Aristotle wrote about tragedy but, although he promised to do it, not really about comedy. Most literary historians say that this was due to his prioritizing tragedy over comedy. I think that Aristotle, despite his genius, just was not intelligent enough to make sense of comedy (to me, the higher form of literature).