Get off my internet
In most of life, but especially on the internet, there’s a disparity between those who have been in a community for a while and the newbies. The more established members, fairly or not, tend to look down on those who are still learning the ropes. It’s easy to forget what it was like to be new and confused and to pass the learning curve off as stupidity. And no matter how careful one is about not falling into the trap of being a smug oldbie, it’s entirely too easy to do.
I’m not sure why communities tend to gang up on others like that. I haven’t really seen an online culture where it didn’t happen. Reactions can vary anywhere from “new people are universally stupid” to “you have a low post count, so I’m going to discount what you say.” Maybe it’s a little extension of hazing, that trial by fire which welcomes people into the community. Those who are scared off by hostility don’t belong, anyway? Maybe it’s just a human tendency towards one-upmanship, to feel superior over someone else even though it’s a petty thing. Definitely something to be aware of when designing communities, though.