What do Hally's conversations with Sam and Willie reveal about his racial attitude?

In Fugard's Master Harold and the
Boys, Hally is a 17 year white boy living in apartheid South Africa.  Two of
his childhood friends are black men employed at his father's cafe--Sam and Willie.
 Through his conversations with Sam, in particular, we see Hally as a conflicted young
man, who is struggling between his love and shame for his father, an
alcoholic.

This conflict is important because it affects
Hally's relationship with Sam and Willie.  When he hears that his father is returning
home again, Hally takes out his anger on Sam, insisting that Sam call him "master."  Sam
warns him that once Hally plays the race card, things will never be the same between
them.  In this way, we see Hally who is not necessarily racist, take out his frustration
on his black friends simply because, as a white boy, he can.  And he does it in a way
that humiliates the older men.

But we also see a naive boy.
 Earlier in the play, Hally acts as if he is open-minded about race.  He seems oblivious
to the inequalities of apartheid. Sam has to tell him the truth about the day that he
and Halle went kite flying.  When Hally had sat down on a bench, Sam said he had to go
back to work.  Sam confessed that the true reason he left was because the bench was
labelled "whites only."  Sam's role as a loyal friend of the family becomes quite clear
through their conversations, and Hally's treating Sam like a servant or worse comes
across as immature and ungrateful.