I realize you are very upset about what happened to you and I am sorry for this. However, you need to realize that you are in the minority. Colonoscopies save so many more lives than those they might worse. Most doctors are doing things correctly. Most doctors are using sterile equipment and most nurses are not eating in the operating room or not using gloves. I'm not saying you shouldn't advocate for yourself or others, but also you should not go making assumptions about every doctor. If you would like to discuss this further, you might want to post on the medical ethics community:
http://www.medhelp.org/forums/Medical-Ethics-/show/684. If you would like to discuss your symptoms and what treatments/tests you should have, then the gastroenterology community here is the correct place to post.