There are different schools of linguistics. The prescriptionists (as the name suggests) try to prescribe one way of language as the only "correct" way trying to stop the changing of the language. Personally I think that the goal of "freezing" a language in one state is not something to be desired and the likelihood of success is about the same as the attempt of trying to dam up the Mississippi with a fishing net. I also think that dialects often tend to enrich a language.
Descriptionists on the other hand (again as the name suggests) describe the way language is spoken.
In case of written language however there are many examples where I agree that language should not be used carelessly in order to avoid misunderstanding. For example some of the internet abbreviations or changes of spelling which don't make a text any easier to understand (while they often look rather confusing).
As for dialects I often wonder what my accent would sound like to "native English ears". In German I speak a mild form of "Ruhrpottdeutsch", the form of the language spoken in the region between the rivers Rhine, Ruhr, and Lippe. The dialect (among other) tends to avoid some plosive sounds (like t) between vocals and certain words are abbreviated respectively combined so it sounds like they were one word. Over here there are so many dialects that some people are even able to tell you what town (e.g. in Dortmund, the town where I was born and spend most of my life so far most people would use the "word" "ne?" for something like the English "isn't it?" while just two towns on, in Essen, they are likely to say "woll?" instead, and in Berlin and some other towns it would be "gell?") you are from when they hear you speak, but with few exceptions (like certain dialects from Bavaria) there are no major problems of communication in Germany.
