They might be experts on the field of rudeness. Therefore they might be right if they consider your posts as rude :p
That makes sense, actually. We do have a few experts here, that can certainly be said. Ahem.
Ok anyway I would say the problem on a forum is that you can't see the face of the poster or hear his voice. So you don't know if he is screaming, crying, laughing or bashing his head into a wall while posting.
There can be misunderstandings and of course there is always sarcasm. One has to be careful about wording, a good intention is sometimes not enough.
Hm. Sure one has to be, but only up to a certain point. "Reading too much into it" is most certainly more easily avoided by the reader, isn't it.
That said, if we are all willing to avoid such flames in the future, both on the reading-before-reply and on the writing side of things, making this subforum more attractive to newcomers should work.