Lol...you guys are blowing this way out of proportion. I've got nothing against Southerners, Northerners, Mid-westerners, etc. We've all got our own local ways of butchering the English language. I just happen to live in the South, therefore I talked about the South. Do people still understand Southerners when they say "ain't?" Yes. Does that make it correct English? No. Do you need to pay attention to the "grammar Nazis?" Well, to answer that, answer this: Do you want the English language to change much more dramatically than it does now every time a new generation emerges? If you didn't have language rules, and people willing to obey/enforce them, you'd have multiple versions of that language. It's a good thing to adhere to the official English language and to try and avoid local versions of it. Local versions will emerge anyway due to human cultural tendencies, but trying to avoid it means that many fewer changes will affect the English language.
@ Sledge: I understand and agree with your view. Don't change based on what other people say. If you respect the English language as it stands, then adhere to the rules. If you think "ain't" is part of the English language (if "isn't" wasn't already present, it would be!), then use it. I don't believe that the manner in which someone speaks denotes his intelligence. An illiterate redneck from the hills can be extremely knowledgeable about many things in life, while a city businessman with two degrees can know only what little he learned to pass college and nothing more. The point here, regarding the English language, is the preservation of the language itself in as proper a form as is possible. Variance over time is inevitable (hence, we no longer use "thee" or "thy"). However, we do need to limit it as much as we can, unless you're okay with basically having a completely different (but similar-sounding) language in 2-3 generations (you won't be alive then, maybe, but it's the principle of the thing).
I know you don't know me personally, Sledge, and that's okay, but I don't get "hung up" on little technicalities like "If he cannot speak proper English, then he must be stupid." We're all individuals and make our own choices. I happen to think that enforcement of the proper use of the English language is very important for its preservation, and therefore I will use it in that manner as much as possible.