Universal grammar is about what language is: it is to be distinguished from prescriptive grammars, often distilled in newspaper columns, which tell us what language should be. We are all entitled to our own opinions of what is appropriate, be it in the arrangement of words or flowers - as long as we keep in mind that these are just opinions. The properties of universal grammar linguists have unearthed, however, are a useful defense when language "authorities" try to rationalize their pontifications: none of the don'ts they advertise can be found in the book of universal grammar.

Language guardians have often blamed linguists as defenders of bad language: moral and cultural relativism is often tossed in at no extra charge. We as a profession are supposedly promoting the idea that anything goes in grammar... But no, we have never said anything goes in grammar. (...) When it comes to the proper use of language, universal grammar is the ultimate authority. It is not about what rules are deemed reasonable or popular; it is about what rules are true. And one sign for a true rule is that it appears in young children, long before they are polluted by dubious grammatical advice.