It's not good forum etiquette to pull somoeone up for spelling/grammar on a public forum. Apart from it causing resentment, the person may have a health problem, is not good with a keyboard, and many people type in 'msg txt' which takes many forms. My spelling/grammar isn't always great on forums, but it is when I write articles as I concentrate more. As long as the message comes across I couldn't give a hoot how they have written it.
On the other hand James, it isn't rude or arrogant, it's just not cricket