I was raised Catholic.
I used to work in a lab and wore a lab coat. In the movie Half Baked, when Thurgood is mopping up in the medical research lab and the one guys says something like "Excuse me Janitor". Then Thurgood replied, "Yes Scientist." I thought it was really funny. Also, I have a Bachelors of Science degree and was working in a lab employing the scientific method, I figured I could call myself a scientist.
WRT evolution, as a Theistic Evolutionist, I wanted a name that reflected that belief, but was also accurate in who I was.
Also, I'm a Gemini and do feel like I have two parts to me. One side is more of a believer and the other side is more of a skeptic, so I wanted the name to reflect them, which usually oppose each other.
I think the EvC debate sometimes boils down to science versus religion. I support both sides.
One thing to note is that I chose Catholic Scientist and not something like Scientific Catholic. I don't think I could reject something that is scientifically sound for a religious belief. I'm a scientist in my beliefs, but a Catholic one, not a Catholic in my beliefs, but a scientific one. I haven't really rejected too much dogma, as I can usually accept both the religious and scientific explanations, because they normally don't seem mutually exclusive to me, and I don't really mind hand waving that much.