The Internet inadvertently undermines the quality of human interaction, allowing destructive emotional impulses freer reign under specific circumstances. The reason is a neural fluke that results in cyber-disinhibition of brain systems that keep our more unruly urges in check. The tech problem: a major disconnect between the ways our brains are wired to connect, and the interface offered in online interactions.
Basically he's saying people are rude on the Internet because we don't get immediate feedback from the person we're being rude to so we don't develop any empathy for them and thence go crashing through the gates of inhibition and off to the Land of Invective. That's an observation people have been making for quite a while, ever since this whole Internet thang got going in a big way. The isolation and anonymity just makes you more likely to rip into someone.
Plus, my own pet theory contributing to this is that people these days tend to treat their written communication as they do speaking. You 'write what you think you're saying' as it were. Trouble is, we think we're also exporting tone of voice and other vocal and visual clues along with the typed words when we're really not. Emoticons and ALL CAPS and italics can sometimes make up for this, but a lot of time, people just don't pay enough attention to how others will actually interpret the words they're writing. Hence, one might think one is making a perfectly humorous, if slightly sarcastic, comment on something someone else has written, which is then interpreted as a slam requiring immediate retaliation. Written communication is, indeed, an art.
So when I refer to post-processual archaeology as fuzzy-headed mentalist claptrap, just throw in some good-natured facial expressions and quit sending email calling me a "*$@% loser of a $)*@&^$* useless piece of $*&@^$ logicial positivist dog*$&%@. So there, you $@($^@(."
Of course, most of you out there don't know this, but the inner voice I was using while writing the above was all done in a French accent akin to Inspector Clouseau.