What three people helped Malcolm into becoming a militant person in The Autobiography of Malcolm X?

We should probably clarify the use of the word "militant"
in the question.  Fundamentally, Malcolm X has to be seen as a leader that advocated
resistance and actively defending oneself in the face of unrivaled brutality from both
institutional means and social means of exclusion.  In this light, one of the most
important people that helped him embrace such a position was, simply put, racist White
people in American society that he encountered.  Malcolm's most basic position is one
where he takes the form of defiance, what one might consider, militancy because he is
exposed to a sense of discrimination and injustice around him.  The Klansmen who killed
his father would be one group of people that convinced Malcolm at the earliest of ages
that violence against Black people was a reality in being.  Another individual/ group of
people who helped to move Malcolm towards a position of active dissent within the system
was the insurance company who would not pay out the settlement to Malcolm's mother,
arguing that Earl Little's death was a suicide, thereby they were not obliged to pay. 
The teachers and individuals on a personal level helped to form Malcolm's opinion that
if he was not going to fight for himself no one else would was confirmed by Mr.
Ostrowski, a teacher who told Malcolm that a lawyer was "not a realistic job for a
nigger."  Rather, Malcolm should be a "carpenter."  In this, Malcolm understands that
the need for active advocacy of one's self and needs must be driven internally, as the
outward social order will not advocate for people of color unless it is to lock them in
a socially stratified role.  These individuals, at an early age, caused Malcolm to
embrace the condition of active defiance that marks his adult
life.