If he doesn't want some form of improvement, then he won't post. Period. If he says that he doesn't want improvement, but posts anyways, then he's either lying or seeking attention.
I didn't see anyone say that he was retarded or that he couldn't speak correctly. I did see some people being fairly rude, and I also saw some people give advice. If he doesn't want people's advice, then he won't take it, but you can't force people to not try to help him improve his writing. You post in this section, and people are going to assume that you would like improvement in some way-- that is one reason why people post here. The other reason is to show people their writing abilities and to try to join the community.