Language is a technology. The goal is communication. Following the rules of this technology - grammar, punctuation, spelling - makes your communication effective. Following the rules is not classist.
It is not classist to follow the rules of plumbing or welding or computer programming. It is simply using the technology to further your ends. If you want to be understood, build a house, or write html you learn to follow the rules.
If you are afraid or arrogant or simply stubborn you can choose to not follow the rules. And watch your house fall down, your website malfunction, and your writings confuse rather than communicate.
Keeping people away from learning the rules of technology is classist. Where the commas go is as important as where they don't. An uneducated populace is the easy one to control. And a poor use of language technology is easy to dismiss.
I would use my very best technology to build my home. Why not use my very best language technology to build and communicate my thoughts and dreams?