The speech is more unfiltered and more expecting of shared values

From "Why People Are Rude Online” and the Audience for Online Speech by Orin Kerr discussing the differences in writing styles in the virtual environment of the internet.

When you write online, in contrast, you don’t see who is reading what you are writing. The audience is unseen and usually largely unknown. This is just my amateurish speculation, but my guess is that a lot of people have a natural tendency to write by implicitly imagining the kind of audience that would be around them in the physical space where they are writing (even though their actual audience is online). Because those physical spaces can be pretty intimate places, such as a person’s home, a lot of people tend to make online communications that use the kind of language they would use when amongst friends. The speech is more unfiltered and more expecting of shared values. When the audience turns out not to share those values, though, they experience the unfiltered speech as rude — which leads them to respond with similar or even greater rudeness. That’s my amateurish speculation, at least.