Everyone here does make good points. Here's my little contribution to the discussion.
I abhor the terms 'literate' and 'illiterate'. I actually think it's derogatory on both sides, since literacy is the ability to read and write regardless of your level of roleplay. Of course, I don't have a clue what sort of terms could be used in place of these, but I still do think it's silly.
Onto the actual matter at hand, I completely disagree with looking down on people with perhaps not as much experience in roleplay as yourself. Everyone is equal no matter how advanced their English is, and I'm genuinely astonished whenever I see people looking down on others.
A lot of the time, mistakes are made on both sides. There are people on either side who reject the other, but I most often see it in those who consider themselves 'literate'. Personally I just think it requires a bit of integration. I picked up my current roleplaying skills from simply watching others, but had I been included a bit more at the time, it might have gone quicker.
Still, I don't think that it's necessarily a problem to begin with. We make it a problem, most of the time. They're having fun and unless it directly affects you, I don't believe there should ever be any issues letting people roleplay however they like. Besides, sometimes trying to correct people can seem very rude, especially in the eyes of whoever you're trying to help. xD