I believe that even if a person has a genetic predisposition to gambling, it is not a particular problem because a person can control his actions and refrain from negative experiences.
In my opinion we choose our own destiny and what to do in life. If a gambler blames his losses on his genes, most likely he is afraid to admit his mistakes and tries to blame someone else for his mistakes.
This is true for the majority of gamblers, they can control their own actions and know when to stop. The problem is however when you become addicted to gambling and lose control of your own actions. It's very hard to imagine such a thing for people who have never experienced or watched an addict. For an alcoholic the rational thing would be to stop drinking, or for a drug addict to buy drugs in the first place. But the brain creates such a strong desire that they can't do anything against it. I am not saying that there is no blame for people with an addiction, it's not the result of a bad gene, they should have been more responsible in the beginning. Once the addiction becomes too strong it's almost impossible to fight it alone, professional help is needed to get the life back in order.