Nerds: Why are otherwise extremely intelligent people so lacking in social skills?

“Normal” people have “tact filters” over their mouths, so anything that comes out of their mouth would be non-offensive to another human being. Thus “normal” people can converse with anyone and not get offended.
Nerds have tact filters over their ears. Thus, no matter what is being said or how offensive it is, it gets filtered prior to them hearing it, and thus they don’t find anything being said to be offensive. Two nerds can be in a room saying anything they want to each other, and neither one will be offended.

The problem arises when a nerd is talking to a “normal” person. The words coming out of the “normal” person’s mouth are filtered, and filtered again by the nerd’s ears, so the nerd does not get offended by what the “normal” person says. However, since the words coming out of the nerd’s mouth are unfiltered (and offensive), and the words going into the “normal” person’s ears are unfiltered, the “normal” person gets offended. That’s where the problem arises.