Doug Semler writes:

Next thing he'll say is "just
because you're smart doesn't mean you have commmon sense" ...

No. First, there's no such thing as "common sense." Second, intelligent
people have reasoning ability superior to that of unintelligent people, since
this ability is one of the hallmarks of intelligence.

*All* groupings based on a demonstrable ability are "self-selected,"
from Mensans to pilots to NFL players.

No. People choose to join Mensa, but they do not choose to be subject to,
say, military conscription.

In other words, it isn't because those
other 119,930,000 people haven't joined because they were denied, it
was because they CHOSE not to join.

Essentially, yes, although it's not a matter of actively choosing not to join
so much as it is a matter of not actively choosing to join.

Most intelligent people don't need the trivial validation that Mensa
membership provides. The ones who do are that way because they've
accomplished so little else in life, in most cases.

AFAIK, there are no secret
meetings where Mensans get together and have orgies or discuss social
dysfunctions. In fact, my only contact with them since I've joined was
to pay my dues every couple of years and read the magazine that gets
sent to my house every month.

Then you need to attend the AGs, where you'll learn about the "orgies."