Madalyn Murray O'Hair (a fanatic?)
"Robert Knowles" 

Fanatic:  A person possesseed by an excessive and irrational zeal, especially
for a religious or political cause.  - American Heritage Dictionary.

Madalyn Murray O'Hair (please note spelling!) has built a fairly successful
family business from her early participation in the court case of Abington
School District vs. Schempp in which William J. Murray III v. John N. 
Curlett was a companion case.  Her various organizations have contributed
quite a bit to the cause of Atheism in the U.S. and the world.  In fact,
several other organizations supporting atheist causes have been formed by
people who were either kicked out of or disenchanted with her organizations.

Her name is practically synonymous with atheism to many people and as a
result, she often gets credit/blame for many things.  One thing that some
people will agree with is that she has a fairly abrasive attitude towards
some people.  In the literature her organization produces, she and her
children often claim that they are the "ONLY" true atheist organization
and that all others are not really atheists (starting to sound a little 
irrational, eh?).  

The history of American Atheists is filled with examples of "purges" of
people who were once loyal followers but somehow fell out of favor
and were banished from the "ONLY" true atheist organization in town.
A lot of times lawsuits are filed against ex-officers claiming that 
their "mailing list" has been stolen.  They often file lawsuits which 
ultimately just screw up the ex-members credit (it looks bad if there is a
lawsuit of several hundred thousand dollars filed against you and you go to
get a car loan!). In fact, if she reads this, she will probably try to sue
me for something, so I have to word all this very carefully.

For an especially intriguing account of one persons wrestle with the first
lady of atheism, I would recommend reading a magazine called "The Match"
published by John Woodruff in Tucson, AZ.  All I can say about it is that
when a local chapter of American Atheists was disenfranchised and several
of its officers sued by MMOH and company, reading this magazine was like
deja-vu all over again.  When you see the pattern it gets a little spooky.

And when you realize how much effort goes into their fight against fellow
atheists it gets a bit ridiculous.

MMOH a fanatic?  I vote yea.