Admins become admins by being asked to do it by the senior/head admins, generally on the recommendation of another admin or head admins. Why someone who was once an admin is no longer an admin is either something personal to that person, or involves clan politics that should stay within the clan. You are certainly free to have your opinion (which I assume is that whoever this ex-admin is should still be an admin, and that some other admins are rude to others and probably shouldn't be admins), but you can rest assured that you likely don't know all of the facts, and that any decision to remove someone's admin rights was never taken lightly by the leadership at XI.
If you have specific concerns regarding COD4 admins and how they talk to other players on the server, then please bring those to the head admin team's attention (unless it's regarding a head admin, in which case take it to the senior admins).