Do also accept his reason for engaging in gambling? Are these casinos right to ban him from gambling?
Whatever reasons he did such thing is between him and his believe. If you ask me wether it's right for the gambling site to ban him, I will say it is within the Power of the gambling site to take any decisions when they see an unusual wining because the reason for any casino is to make money and not to get into bankruptcy.
He must thinks twice before he continue playing gambling because his position as a religious leadership. He can makes his followers doing the same as what he did and when those people can not holds themselves in gambling, many people will becomes addicted to gambling and even he will becomes addicted to gambling.
Casino site can not ban him as he is just a user and will lets him still playing gambling so that needs his awareness to consider what the meaning of gambling for him. He must realizes that gambling will not gives money for him easily and he can lose his money anytime.
But he should not gamble to make money and needs to find out the other ways to have money for his plan. Many people may do something to helps him, especially if he have a good plan that wants to helps other people.