Q: Is there an ethical reason to support Open Gaming?
A: In this writer's opinion, yes there is. It has been an established feature of RPGs since their inception that they should be used to create new content. Prior to the advent of widespread Open Game licenses, there was no practical way for that kind of material to be legally and widely distributed.
Open Gaming is recognition that your natural human right to free speech is protected and enhanced. The Open Game system is a way for the game publishing industry to finally deliver on the basic promises made by the very first RPGs; that individuals should be free to copy, modify and distribute their own creative works derived from the game systems they have acquired.