Some people think they can get away with everything because it's the internet *shrugs* Personally I dislike those didn't read comments because those are actually spam and well, if you don't read it, then don't comment -_- If it's only because of post raising, they can go to the forum games.
Anyway, don't think about it too much, I'd say. There are always going to be rude people, both on the internet and the real life.
Your friend can also post his fanfiction on fanfiction.net ^^ Most people there are very friendly - I've been on that site for four years now, and writing stories for it for three and a half years and I met some really good friends on it. So maybe that's an idea for your friend? Just a suggestion ^^