Anyhow, I doubt we can keep this on topic, but I suppose I can try...
I actually find that I need to be more polite on the internet, since due to the fact that emotions rarely can be effectively portrayed through text(since you are missing vocal tones and other body language), people tend to either take jokes seriously or take serious stuff like a joke. I find that this leads to a lot of people being labeled as trolls or jerks, since they are joking around, however being that a lot of people miss that(since it is really easy to miss, especially if one is tired or something), it ends up hurting other people. Being that they are actually hurting people they certainly deserve the label, but I doubt they actually intend to do so, rather it is a simple oversight which they need to correct.
When physically talking to people, there is usually sufficient information from body language that it is realistically possible to discern whether or not they are serious. Also, when people know someone fairly well, they can also tell whether or not they are serious, since they learn that from experience with that person. I find that this tends to lead to them standing up for the offender since to them it was obvious that they were joking.
/opinion
But yeah, I try to be as polite as possible, both in real life and especially on the internet.