Anyone who bets against "Leslie will take X action" when Leslie can participate in the betting is, indeed, a real loser.
The problem I have with people who think compulsive/poor gamblers only hurt themselves and just "get what they deserve" is that compulsive/poor gamblers steal money from people around them to feed their problem/disease, and also have dependents who are in no position to shield themselves from the consequences of those actions.
As usual, if every person was an island, life would seem much more "fair" and simple, but people are not islands. As a society, we hold immense value in being able to do certain drugs, and so fine, we accept that collateral damage will occur. But what is the societal upside of allowing a company to exploit "real losers" in this case?