One of my favorite lines from the Harry Potter series is when Hagrid says "I am what I am an' I am not ashamed". I think this is a great message for kids to inspire them to be who they are, and also not to pick on other people because of who they are.
Hagrid has a sense of pride in being who he is, no matter what others think of him. Another good line is when Sirius Black says "if you want to know what a man's like, take a look at how he treats in inferiors, not his equals".