Pretty much everything that he says speaks to my point. He's talking about illegal gambling, getting in trouble with the mob, owing debts that you can't pay and needing to find a way out, etc.
You don't have integrity monitors flagging bets from stuff that the mob is getting down on thru illegal channels. With legalized books, you do. Guys placing these bets at legal US sportsbooks is what uncovered it all. And people making legal bets are posting their $ up front, and not getting into a situation where they owe 6 figures to a bookie and they need to either find a way out of it or deal with threats of violence.
To me, the legality itself isn't an issue...in many ways, it's a solution to bring more checks and balances into play (and raise tax revenue for $ that would otherwise be going offshore or into criminal hands). Aspects of it certainly bring about more issues...the micro-bets, the advertising (I'd certainly be fine with more restrictions on it), etc.
I certainly come at it from a biased point of view (gambling is a source of income), but I think many have such a negative view of gambling that they miss the positives that legalization has today...if the Terry Rozier bets were placed thru Costa Rica, he's likely playing for the Heat tonight and no one knows anything about this.