How are Lieutenant Kotler and Father opposite with Bruno?

In John Boyne's The Boy in the Striped Pajamas, Lieutenant Kotler treats Bruno differently than Father does, even though they both seem to be fairly strict. First of all, Father loves Bruno because they are family; however, Lieutenant Kotler, who works under Father as a soldier, seems to act like a neighborhood bully toward him. For example, when Bruno is upset about the move from a lovely home in Berlin to a humble home...

In John Boyne's The Boy in the Striped Pajamas, Lieutenant Kotler treats Bruno differently than Father does, even though they both seem to be fairly strict. First of all, Father loves Bruno because they are family; however, Lieutenant Kotler, who works under Father as a soldier, seems to act like a neighborhood bully toward him. For example, when Bruno is upset about the move from a lovely home in Berlin to a humble home in Auschwitz, Father listens respectfully to his concerns. Then Father says the following:

"Just settle into your new home and be good, that's all I ask. Accept the situation in which you find yourself and everything will be so much easier" (53).

In chapter 7, Bruno interacts for the first time with Lieutenant Kotler and goes away unimpressed. Kotler does not seem to be very mature for his status as a Lieutenant because he teases Bruno and won't give him straight answers. Also, when Kotler tells Pavel to assist Bruno with finding a tire for a swing, he condescendingly speaks with slurs and a harsh tone. Later on, in chapter 15, Kotler's teasing makes Bruno infuriated as follows: 

"Bruno narrowed his eyes and wished he were taller, stronger and eight years older . . . It was one thing, he decided to be told what to do by Mother and Father--that was perfectly reasonable and to be expected--but it was another thing enirely to be told what to do by someone else. Even by someone with a fancy title like 'Lieutenant'" (165).

As shown above, Lieutenant Kotler acts immaturely and like a bully with Bruno and other people; whereas his father, on the other hand, treats his son with dignity and respect even though he may also be strict. As a result, Bruno appreciates his father, but he does not appreciate Lieutenant Kotler.