As a bit of a counterpoint to my previous post in this section, let me broach a topic that is also impossibly stupid: Proper English. Proper any language, really, including those wacky French with their use of courriel instead of just adopting email. I guess nobody told them that there was a difference between being cultured and sophisticated, and just being a pedantic dick.
The purpose of language is (or at least should be) to convey ideas. For that reason, I'll take issue with inserting empty words like actually, but I don't take issue with slang or “dirty” words, so long as they're used with purpose. I don't even take issue with words that are used with a non-tradational meaning (e.g., “Dude, that was sick!”).
Linguistics is a far more reasonable approach to language. Instead of pretending to preach from on high what structure is “correct”, you look at what is actually in use for communication. You consider the data first, and only then can you determine what is Proper English. As my Pappy once jawed, “I reads me some Shakespeare 's'boy, and y'all ain't soundin' nothin' like that.”