Playing the devil's advocate: Wouldn't Blizzard make more money if they DID NOT ban botters?

I was debating with a friend the effect bots have on Diablo's RMAH and the in-game experience. Let's start with in-game. Unlike bots in MMOs (such as WoW), in Diablo you rarely see bots as they are safest to farm in non-public games. Even if bots did join public games, you never have to see them because you can always create your own private games. Therefore, bots don't really affect the in-game experience.

However, they unquestionably affect prices of the gold AH and RMAH. My friend and I argued Blizzard's interest. In an ideal world Blizzard would make every effort to ban botters because, simply, it's cheating. It's unfair. It's not in gaming spirit. In WoW botters are banned because they are an eyesore, can affect the in-game experience directly, and negatively impact someone's perception of the game and cause Blizzard to lose subscribers.

Diablo is not a subscription game. You could certainly argue people will quit Diablo over botting, but I doubt anyone would not buy the game because of botting -- simply because a potential buyer would not know botting even exists until they purchase and play the game.

Now the crux of my argument: Blizzard makes money off RMAH transactions from botters. Blizzard has nothing to lose by NOT banning botters. Their customers have already paid for the game. The only counterpoint I can think of is people who quit the game will no longer be providing Blizzard money through the RMAH. However, I highly doubt anyone is quitting the game because of bots. Bots effect on the economy is certainly real but at the same time hard to perceive or extrapolate, and they have virtually no affect on the in-game experience as I explained earlier.

tl;dr: I love Blizzard, but I see no incentives as to why they would ban botters. Don't get me wrong, I absolutely dislike botting, but from a profit standpoint Blizzard can only make money by letting botters exist. I realize they are announcing bot ban waves, but the devil's advocate makes me think they're not really as invested as their PR may make them out to be.