The positive for the exchanges would be?
Well the exchanges like them, bots pay fees too.
The reason other then pure greed that they exist?
Correct, but it's the same reason that motivates human traders too. And the greed always starts in the mind of the human.
Can anyone come up with an legitimate negatives to them being removed from practice?
I really do think they add depth and stability to the market. Bots are unfeeling and logical. The only trouble comes when all their stop losses kick in at once, but the same is true for human daytraders too.
I can't see any firm logical argument against bots? Am I missing something?