The Power of Imperfection
In the times of the Holy Temple, the chatat was an offering brought when a person inadvertently transgressed. There was a special prohibition against its meat being removed from the Temple. If, however, the High Priest brought a chatat for his own transgression, its meat was taken outside of the Temple and burnt.
The Oral Tradition gives a reason for the difference.
The meat of a regular chatat was not allowed outside the Temple, so that people would not ask questions and find out who had transgressed. This was in order to protect individuals from the shame of others finding out what they had done. In the case of the High Priest, however, the Torah wants to publicize his transgression - to make the point that no one is above the law.
I believe there is another message here. The Torah wants the world to see that even the High Priest can transgress. He is not an angel, but a human being. And as such, he is subject to the same desires, selfish motivations, and bad character traits as anyone else.
In a similar vein, the Talmud tells us that a Jewish sage should be "tocho k'baro," his inside like his outside. It does not say that he should be "perfect" both inside and out. It just says that they should be the same - no pretending, no covering up. If there are imperfections on the inside, a Jewish sage will not pretend to others that they are not there. He will accept them and strive to improve them.
It's much more productive for us to see that our role models make mistakes than to believe they are prefect. It releases a lot of unhealthy pressure when we know that we are not the only ones who are doing things wrong. If we look around and think that our role models are perfect, we will never hope to attain their levels. When we realize they are human, however, we believe we can get there, too. When the High Priest's offering is burned outside the Temple, it is a public reminder that even the loftiest spiritual levels are available to each and every one of us.