English vs Yanglish

The NCTE Beliefs about the Teaching of Writing state that "Conventions of finished and edited texts are important to readers and therefore to writers."  This inspired a conversation in class as to whether or not writing that didn't follow the conventional rules could be read, understood, or enjoyed.  Personally, I disagree with this statement.  I believe students should experience writing in many different voices and have the opportunity to write in the voice they feel comfortable writing in, while still learning about the standard conventions of writing.  And besides, The Color Purple is one of the most beautiful books I have ever ready and no one can or will tell me it is not to be understood or enjoyed.