> There is arguably something of a correlation with the tact filters, come to think of it. People who have the tact filter installed in the picked-on-nerd direction will just go ahead and do or say something, assuming that other people will ignore them at their own discretion. People who have the tact filter installed "correctly" will feel presumptuous participating somewhere where they think they shouldn't, absent a clear statement that they should.
I think you are correlating to somewhat unrelated things
1. the filter direction (and the probability of feeling offended)
2. reluctance to participate.
I have seen a lot of people with their tact filters in the "correct" direction who can be extremely pushy about getting involved with something, so I don't think this is a very good correlation.
The "tact filter" explination does go a long way towards explaining the offense that some people take over comments that were not meant to be offensive. Not just related to "nerds" but also in other fields