Paul, thanks for setting off an interesting discussion.   And thanks especially for demonstrating exactly what people should do when they feel the urge to ask, comment or otherwise weigh in on something here.  Sign right up for your copublisher account and jump right in.  Welcome to the Narcosphere.  
I must admit I do like the word gringo.  It doesn't bother me in the slightest to have it applied to myself or people like me.  That plus finding it pretty useful as a word make it easy for me to like.  
Is gringo racist?  Well, maybe there's a test for that.  Imagine two obviously gringo ex-pats had a child in Mexico.  23 years later, Baby Hypothetical has grown up entirely in Mexico, living as a Mexican, fully absorbed in Mexican culture.  Is grown up Baby Hypothetical a gringo?  My guess is no.  If Baby Hypothetical gets called a gringo, it's probably just teasing, misidentification or something based on some very gringo-like trait that Mommy and Daddy Ex-Pat managed to instill upon their child.  I welcome anyone who knows someone like that to correct me if I'm mistaken.  
Can gringo be racist?  Sure.  But that's not saying much.  I've heard every single descriptive term ever concocted to denote black people used as a slur against black people.  Is African American racist?  No, but around these parts when you hear an extra long pronunciation of the 'A' in 'African' coming from 'white' lips, sometimes it is.  It's a reality here that says something about race relations and language both.  
Chicano poet Ricardo Sanchez described how he grew up hating the gringos in El Paso in the 50s.  Later he came to realize that his hatred, which some would call a kind of racism, robbed him of a portion of his own humanity by preventing him from seeing the humanity of others.  Whatever it is that lessens our humanity; that limits our humanness; must be struggled against.    That I believe as much or more than anything.  But from knowing racists of many varieties I'm convinced that it's not a word, but a conception lying behind a word that must be struggled with.  
Is gringo a useful word?  Perhaps Paul is right to suggest the spanish lexicon is chock full of superior terms.  My own spanish is terrible, so I wouldn't know.  But I can't think of another word that conveys the same meaning as gringo.  What other term for "Americans" or "Westerners" implies not just a lack of understanding but, as Judith described, a significant cultural obstacle to becoming able to understand?  If anything, in our present days, gringos really do need to be reminded that not only don't they get it but even with some effort they might never get it.  The first step to understanding is being cognizant of a lack of understanding.  And, unlike the new and unusual trivia Mr. Melcançon's textbooks describe, authentic journalism must be about increasing understanding.