Ok I'm not sure of your type OP, but I've seen a lot of this from INFJs, especially. I majored in English Literature and maintained a 3.9 GPA, belonged to several honor societies, and minored in French. However, I really am not a grammar maven. I value content over form.
I am disturbed when people are so ignorant that their writing is illegible or apparently illiterate (excepting cases of people who have a different mother tongue, particularly when that mother tongue utilizes a different alphabet) but I consider Southern dialect and Internet speak valid forms of language.
I'm not offended by the degredation of language in chat rooms or even what is spoken by lolcats because those are simply dialects, and all languages have various dialects. Languages also tend to change form, shape, and spelling over time.
Have you taken the history of the English language? Did you know we share a common ancestor with Slavic languages? It's absolutely mind boggling. If you go past middle English to old English it's shocking, let alone tracing our linguistic roots to parts of Iran and Russia.
Anyway, sure, it sucks when people are completely ignorant of how to properly use their own language in the written form. However, remember it's just your skill set, and the people who don't know how to properly use "your" and "you're" might excel at maths.