I don't see where the last statement fits on the overall of your message. The point is that proper grammar and spelling is important in writing for newsgroups, webpages, letters to the editor, etc. because you don't personally know your audience. Slang and abbreviated writing is appropriate for friends and acquaintances. If a statement is writen with speeling mestakes and gramitckal errors, you mite git the meening, however, the messige is not as affective, or smoothly redable.
Poor writing is equivalent to someone speaking with spinach stuck between their teeth.