@kentuckycat - You are correct. That particular Family Guy episode showed the main character's irrational fears of having a prostate exam and not being well informed of what it actually was. In the episode he sued the doctor for sexual harassment, then had to have a prostate exam in the end because he started to have a problem, showing how irrational and silly his fears were.
The point of the whole episode was to show that no one really has anything to worry about with a prostate exam or any type of exam involving the anus. It is simply mental taboo to let someone else examine your anus but when it is necessary a doctor has to in order to diagnose a potential medical problem. It is irrational for someone to let their unnecessary fears get in the way of having their health properly diagnosed.