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.
Charles Yang, The Infinite Gift: How Children Learn and Unlearn the Languages of the World
language, language-acquisition, universal-grammar