I can be quite picky when it comes to deciding who I roleplay with. I'll roleplay with literate and semi-literate users, and by that I mean people who type in full sentences, use grammar and punctuation, and type words properly instead of short-hand. But I'm not so picky that if someone makes a typo or something I have a major go at them; I appreciate that everyone has their own RP style, and everyone, even the 'best' roleplayers, make mistakes like typos, missing words out or forgetting or put a comma somewhere. We're only human!
I also respect illiterate roleplayers. Even though I might not want to RP with them, I don't hate them for being illiterate. There are many reasons why a person might be illiterate, I'll name some: young age (like primary school age), learning difficulties, lack of experience, and English not being their first language. I think people who verbally abuse illiterate people should be more considerate, because, unless the person specifically told you, "Sorry, I'm illiterate because [reason]," you don't know for sure why that person isn't quite on your level. We all started off illiterate at some point, I'm sure of that.
Thankfully, I've never been beaten up on my roleplaying style, but I have been corrected one or two times. And I don't mind that, I like critisism so that I can learn from the mistakes I make, learn new vocabulary and stuff. I'm 18, passed GCSEs and A levels, and still my English isn't perfect. It is apparently one of the hardest languages to learn and I think that should also been taken into consideration before you decide to critisise someone.