Personally I have no idea if some topics could istigate more or have a detrimental effect on a gambler.
In any case, what I've seen have right for an approach with a gambler is:
make people reflect on the real statistics/probability of events.
ask an inveterate bettor to list his income and expenses and from there understand if this activity is worth it
This decision unfortunately is on the gambler himself. If he is determined to change, he can change for himself.
But of course, as much as possible he needs support from his immediate family as much as possible.
As he can easily divert himself to the old gambling life, he always need assistance from somebody close to him.
It's not easy to quit gambling as an addict. Is just like quitting smoking as a smoker. That is why is better not to become a gambling addict. Quitting gambling as an addict needs an extra job and strong determination by anyone involved.