I know this sounds odd, but how do you delete a race that you accidentally created and don't want to be in the game when you select random races?

What I mean is this. When I first started playing I would use an existing race but give them a different name or picture. Now, when I get to the choose opponents screen, those additional races are available. For example I have the Dominion of Korx but also the Korx Traders that I played as one time. And I don't want to start a new game with random AIs and have two Korx races, which has happened. I go and try to "clear" the race - it reverts back to the original name, but when I get to the selection screen, it's back.

I know I can just hand pick the races but I like the random option.