The term "evolutionist" is a person who believes in evolution. That would include geologists, botanists, zoologists, marine biologists, archaeologists, astronomers, physicists, and cosmologists alike. To say "geologists" only study the Grand Canyon only excludes evolutionists if all geologists were creationists, and that is not true.
In the context of this board, "evolutionist" is used interchangably to refer to people who oppose creationism in debates; as well as biologists who study the development of life.
The point is that the Grand Canyon is not relevant to the theory of evolution, which is only concerned with explaining the diversity of life we find today. The Grand Canyon is relevant to geology, and the big separating question in geology is "how old is the Earth". It is possible to believe in an old earth and not be an evolutionist (i.e. you take a position of an extremely old earth, but all the life on it is 6000 years old and created by god.)
Thus, refering to a geologist who believes in an old earth as an "evolutionist" is not really correct. You oversimplify the debate if you polarize it into only two positions. (Consider Salty on this board, who is no YEC, but not entirely an evolutionist, either.)
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