It will not help. It will just encourage illegal gambling.

There's actually a good solution to this, and that is to increase the taxes from those who are running the business and not the players. That way, there will be fewer online casino providers in the country.
Making it illegal will simply lead to more online casinos going underground, which in turn means more scam websites that will only last a few weeks before disappearing if they sense government scrutiny.

IMHO, they are not doing it diplomatically. There's always a way to discourage people and businesses from gambling, and that's if it becomes more expensive.