I was one of those guys at one time too. I remembered my grandpa(who collected Morgans) telling me very seriously as a child never to clean a coin. When I began collecting again as an adult one of the first posts I saw on an ancient forum was some guy taking an x-acto knife to a bronze to clean it and I was shocked. I learned pretty quickly exactly why this was the norm when I got my first uncleaned coin but I was still surprised that anyone could do that to a coin and not destroy its value.