All people have a "tact filter", which applies tact in one direction to everything that passes through it. Most "normal people" have the tact filter positioned to apply tact in the outgoing direction. Thus whatever normal people say gets the appropriate amount of tact applied to it before they say it. [...]
"Nerds," on the other hand, have their tact filter positioned to apply tact in the incoming direction. Thus, whatever anyone says to them gets the appropriate amount of tact added when they hear it. [...]
When normal people talk to each other, both people usually apply the appropriate amount of tact to everything they say, and no one's feelings get hurt. When nerds talk to each other, both people usually apply the appropriate amount of tact to everything they hear, and no one's feelings get hurt. However, when normal people talk to nerds, the nerds often get frustrated because the normal people seem to be dodging the real issues and not saying what they really mean. Worse yet, when nerds talk to normal people, the normal people's feelings often get hurt because the nerds don't apply tact, assuming the normal person will take their blunt statements and apply whatever tact is necessary.