Explain the theme of fanaticism in "Things Fall Apart."What are exaples in the book that show the theme: people who adhere fanatically or...

I disagree with this as a theme present in the
novel.

In Things Fall Apart, both
cultures (African and British) adhere fanatically to their respective cultural values,
but it is not "adhering" to them that brings disaster.  Instead, both cultures foresake
their cultural values for selfish values.  In the end, the cultural values are not to
blame: it is the individual who gives them up.

Okonkwo
breaks his Igbo cultural values repeatedly, which leads to his own exile and death.
 During the Week of Peace, he beats his wife.  When told not to take part in the killing
of Ikemefuna, Okonkwo slays the boy himself.  Knowing that his tribe is clearly
outgunned by the British colonists, he nonetheless kills a British messenger, inciting
more violence.  All of Okonkwo's tragic flaws lead to his personal disaster, but I am
not sure they necessarily lead to the disaster of the tribe.  That was
inevitable.

The British, too, make the same mistakes.  They
govern, proselytize and colonize a people without understanding the Igbo cultural
values, or their own.  They treat the Igbo religion as superstition and their polygamy
as a sin.  Instead of adhering to their own cultural or Christian values, which stress
tolerance and freedom, the British institutionalize the Igbo people.  The British
Christians beat prisoners and burn churches.  How are these their culture's
values?

The point of the novel is that both culture's
values were undermined by other forces (technology, institutions, modernization,
politics, and greed).