In Into the Wild, why did Chris McCandless try to evade all emotional connections with people?

That is a question that does not have a certain answer;
the reader must simply take what information he is given about Chris and draw his own
conclusions.  Chris was raised by parents who were far from perfect.  He felt greatly
wronged by them and was apparently felt so hurt and betrayed by them that he allowed his
emotional injuries to push him away from being able to trust and have faith in his
fellow man.  In general, Chris felt that, as a whole, society is wrong in its approach
to life; he felt that people should live free of the constraints and desires (material
possessions, status, etc.) that most people subject themselves to.  Basically, he felt
that there was little or no truth in most people and their lives, so he did not wish to
subject himself to what he felt was wrong.