Yes, the judge will be swayed to judge against your son if he doesn't have an attorney representing him because it looks bad on the judge when he has to convict a member of the poor class because they're criminal as a result of their poverty, but the judge won't come straight out and admit it because that would prove his judgment is biased.
I think you were invited because without an attorney, a judge can get an idea of why a defendant is the way he is based on his parents appearance and behavior in a courtroom environment. People with weight imbalance represent a chemical and therefor biological, or psychological imbalance. After accusing someone of being a criminal, the justice system would aim to send an individual ultimately to a mental institution for failing to assimilate a brainwashed, fear-driven society.
Study the books in your local LAW LIBRARY and ask questions at the Reference Desk. Your public library is likely to have the books you need checked out if you live in a highly populated area; however, it wouldn't hurt to search your public library database online before going, but there is also a chance you could come across a book that may help you that you couldn't browse through online without checking it out (assuming your library permits online item reservations).
Distinguish the sides of your argument that are personal feelings, emotion and exclude that aspect of your argument for the remaining provable facts. One trick a judge used to find me guilty when I was innocent, represented myself in court and despite 2/3 testimonies in my favor; I told him that he had to find me "Not Guilty" because there was reasonable doubt to believe that I was at fault; his reply was "they teach us that (trick) in law school". His education didn't preclude my innocence, but I think I was found guilty because if he were to have judged in my favor - he would have (in theory) earned the votes (that you get when you're running for a public servant servant such as a judge) of only myself; however, in judging against me he earned the approval and (political) support of my opponents represented in the courtroom that were there litigating against me. It's impossible to prove judicial bias without hiring private investigators to trail your judge, your accusing officers, your witnesses and the plaintiffs most likely, without interfering unlawfully.
Live life walking on eggshells; people are itching to throw their fellow human beings in jail so they can have this world all to themselves.