Obviously OPA does not interpret it as you do.

Where's the difference of predudice of people of color or race, or people that own utility trailers when making the statement that property values are being lowered?

You are seriously trying to make some equivalence between discrimination against people because of their race, color, creed, sex --- and a belief that big utility trailers in driveways lower home values?

Prejudice against PEOPLE is a legal issue; prejudice against trailers, trucks, buses, etc. parked in driveways in a covenant restricted community is not a prejudice against people. I am also prejudiced against four foot weeds in yards. 

In my opinion tall, weeds, trailers, trucks, food trucks, buses, etc reduce home values. You are certainly free to think otherwise. If you think OPA should allow large construction utility trailers go seek an exception and/or a change in the Guidelines. That should prove interesting.