How much should we "dumb-down"?

When I decided to leave engineering for health care, I took a year long anatomy and physiology course at the University of Colorado. Since I was late in applying to school I had to get on the "wait" list for the class. There were 300 people in the auditorium when I went to the first class!
I asked the professor after the first lecture if there was any real chance to get in the class. He, told me to wait until after the first exam and there would be plenty of room. He was right. After the first exam over 50% of the class dropped since it was so hard.
When the professor was challenged about how difficult the exam was he responded " So many of you want to be doctors. If I ever have to go into surgery and one of you are the surgeon I will be very comfortable knowing you know your A&P.".
This is how I run my classes, they are for people who are willing to push themselves to learn what they don't already know.
It seems like we--this is the collective we of people who instruct others--try to dumb things down so much that I wonder if we know what we are talking about. This will only harm the field of animal body therapy.