There's a recurring joke that proceeds along these lines:

What do you call someone who speaks two languages? Bilingual. What do you call someone who speaks just one language? American.

Sometimes, the reference is instead to the British. But let's consider the reality that lies in back of this joke.

The vast majority of people who are bilingual speak English as their second language. Why English? At base, because of the economic significance of those who speak English, especially of those for whom English is their native tongue. This significance originates in the past scope of the British Empire, especially in North America. The American economy was once the world's largest — at the present, the matter is muddled — and the combined size of the American economy with that of other primarily Anglophonic regions still exceeds that of the Sinophonic[1] or Spanish-speaking regions.

If no language had something like the economic significance of English, then most people who are now bilingual would instead be monolingual. As it is, they had good cause to know English, but it wasn't their first language, so they learned it as their second.

Thus, mocking people for being strictly Anglophonic generally amounts to mocking them for having been raised amongst the peoples of the linguistic group that has the greatest economic significance. It would be actively stupid to mock them deliberately on this score, and doing so thoughtlessly is not a very great improvement.

(I'm certainly not saying that there are no good reasons for those who know English to learn other languages.)

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[1] It may also be noted that the differences amongst what are called dialects of Chinese are often greater than the differences amongst what are regarded as separate languages. These variants of Chinese are labelled as dialects as part of a more general effort to create an illusion of national unity. Mandarin is a widely spoken language, but Chinese is really a family of languages.