Interesting question, but it's complicated by the fact that an even more polite society, Japan, is said to have an even more polite internet. More anonymity, more group bonding, more political deference, when your theory would predict the exact opposite.
I'm not sure that this is entirely the case. 2chan has been quite disruptive to the culture. Its enforced anonymity and subsequent freedom from personal societal retaliation is a very new phenomenon there.
Except for the anonymous super free-for-all sites, like that one where you can write over images and video. I recall reading an article about a lady celebrity there who was trying to identify people smearing her online, to sue them. (Hadn't succeeded at time of writing.)
