I agree with you, however, little children should not be on FH, considering you'll find a lot of rude and inappropriate members on.
As I joined when I was 12 (possibly 11, cannot remember clearly), I observed other's without asking them for a demonstration and got to learn the differences between illiterate, semi-literate and literate. Also, people get a fair education on grammar and spelling in general, since that's what you should start off with any school.
But indeed, newcomers will find it difficult to adapt and learn proper literacy, but I can see why these people get annoyed with them. Most of them - not all - often territory claim, or break the rules in many ways. Especially when you find Literate role player's being approached by illiterate Warrior Cats and starting off a very tedious and unnecessary fight.
Also, there are plenty of Illiterate members coming into some of my groups, and when I ask for an RP sample, they start to fuss and get angry because they do not know what it is, even when I explain it to them. Some people who have grown up with the English accent cannot even string a simple understandable sentence together when they're 15. Thats generally why people look down on them. But I agree with you on the case of being overly rude to newcomer's, since they'll have a hard time to understand any sort of literate roleplay.
I think there should be official Role-play helpers on FH, just to get people started and understand things in a less brutal manner.
Thank you so much for posting this rant, it's quite an important topic. xD