Al,
It happens to the best of us, and it's a big man that steps up and says sorry publically.
Public forums are a bit of an art form, as there is no facial expression or tone of voice to go with our typed words. People can come across more aggressively without meaning to, and it's very easy to respond in kind.
I try to post with the mindset that the person reading it could reach out and pop me on the nose if I annoy them sufficiently, and I find that helps. Of course, sometimes I get annoyed enough myself to invite it, but that's life!
Cheers,
Bill