Why doesn't Bruno like Lt. Kotler?

Lt. Kotler is
the stereotypical Nazi officer from concentration camps: He is brutal, sadistic, and
opportunistic.

From the first time that he has encountered Lt. Kotler coming
out of his father's office, Bruno feels a certain discomfiture in his presence. In Chapter 7
when Bruno wishes to make a swing, he asks Kotler who is talking with his sister Gretel if there
are any old tires that he can use to make a swing. Kotler calls to the prisoner Pavel, who works
in the kitchen in a biting voice, using a pejorative term for Jews as he does. He orders Pavel,
using a very pejorative term, to take Bruno to a storage shed where there are some
tires. 

Further in the narrative, Lt. Kotler is invited for dinner and when
Pavel tries to pour wine for him, his hands shake so badly that he spills some of this wine on
Kotler; Bruno witnesses the enraged young lieutenant react violently to Pavel. Then, in Chapter
15, in preparation for a birthday party for his mother, Shmuel is brought to the house to clean
and dry some very small glasses because Pavel's hand is too large. When Bruno sees him there, he
is happily surprised. As he talks to Shmuel, Bruno eyes some chicken in the refrigerator; he
takes some offers three pieces to his friend, who is at first afraid to eat it because of Lt.
Kotler, but his hunger persuades him to gobble some down, anyway. Unfortunately, Kotler enters
the kitchen and accuses Shmuel of eating. Shmuel tells Kotler that Bruno is his friend and he
offered the chicken to him; however, out of fear Bruno denies knowing Shmuel or having given him
any chicken. After this incident, Shmuel is missing when Bruno tries to apologize by going to
the fence where they meet; several days later, though, Shmuel appears with terrible bruises on
his face. Bruno suspects that the brutal Kotler has inflicted punishment upon poor
Shmuel.

Also in Chapter 15, Bruno has several specific reasons why he detests
Kotler:

1. Lt. Kotler never smiles; instead, he appears as though he
   figuratively "was trying to find someone to cut out of his will."


2. Whenever he addresses Bruno, he calls him "little man," and Bruno resents
   this because he is uncomfortable about not having yet had his growth spurt.


3. Lt. Kotler seems to always be in the living room joking with his mother who
   "laughs at his jokes more than she laughs at Father's."
4. Whenever
   his father is called to Berlin and is gone overnight, Kotler is at the house, acting as though
   he is in charge. There is obviously something going on between Bruno's mother and him because
   Kotler is at the house even when Bruno goes to bed at night and "in the early morning
   before he wakes up." Then, one day Bruno hears his mother call Kotler "precious"
   as she tells him she has some free time then, but she stops short of saying more when she sees
   Bruno. While Bruno does not comprehend the sexual implications, he resents his mother's
   affection for Kotler.
5. When Bruno has Treasure Island
   under his arm one day, Lt. Kotler asks where he has procured this book, but he does not pursue
   this topic when told that Bruno's father has given it to him. However, the cruel officer takes
   the book and holds it above Bruno so that the boy cannot retrieve it. Nevertheless, Bruno is
   quick enough to grab his novel when he can reach it.
6. Bruno resents Kotler's
   supercilious tone of speech to him.
7. Bruno does not like Kotler's talking
   and joking with his sister Gretel.