Steve Foley writes:

My experience is exactly the opposite.

Where does your information regarding 'Almost all Mensa members' come from,
and how do you define socially dysfunctional?

I know many members of Mensa, and I've dealt with others indirectly. Almost
all of them have "issues" when it comes to human interaction. Very often they
have not been as successful as they'd like to be in one domain or another, and
joining Mensa seems to be an attempt at validating themselves in some way.
People who are smart and successful don't need to join Mensa to feel good
about themselves; people who are smart but have nothing else going for them
tend to be strongly attracted to organizations like Mensa.

There are normally adjusted Mensa members, but they are rare. Most of them
are geeks in some (negative) way.

The other high-IQ clubs are much the same.