In what ways does Steinbeck warn us about the extremely destructive nature of mankind in Of Mice and Men?

The two characters who end the novel might be a good
insight into this.  Carlson and Curley are destructive in their own right.  Curley, the
little guy always looking for a fight, and Carlson, who represents' Yeats' idea of "the
worst are filled with passionate intensity," are both representations of how destructive
individuals can be.  The incident with Candy's dog reflects how there is a destruction
intrinsic to man.  Carlson being insistent on putting the dog down and creating a
defense for it, while the dog's owner looks on for someone, anyone, to stop it.  When
Steinbeck describes "the silence" between the time Carlson takes the dog out of the
living quarters and the time he shoots it dead, there is a level of destruction
completely apparent within human beings.  While Carlson and Curley represent destruction
in its most malevolent form, there might be a statement about how human beings destroy
in the form of Lennie, himself.  Lennie, whose heart is pure and whose childlike nature
is above reproach, is incapable of doing anything with his hands except demonstrating
brute force.  He kills the animals he pets with his hands, and kills Curley's wife by
touching her hair and then crushing her, breaking her neck.  In the end, the destruction
that is wantonly apparent in Curley and Carlson is a significant element to the
destruction that is within mankind.  Yet, the unintended destruction that is also
evident in Lennie is also a part of what Steinbeck suggests means to be
human.