Most internet sites have them – users who are downright rude, nasty and offensive to others.
What’s worse is when a user clearly knows the subject matter but is still rude, nasty and offensive to others. Others who also know what they are talking about can recognise their advice as being correct, but because they don’t explain themselves they just come across as bitchy and uninformative to learners.
There’s one particular user like this on http://stackoverflow.com/ – many times I’ve seen a question with a bitchy comment from them. It’s even worse because that’s a site people are meant to learn from – yet their uninformative, bitchy approach makes that impossible.
There’s no other way to end this than with a plaintive cry of “Why can’t people just be nice to each other?”