It does becomes a choice when you're still in the right mind of yours. But when you're already hooked, do you think that you'll still be able to control yourself from such? I don't think so. That's why it is no longer a choice for those that have already been addicted, they have no choice and they can't help themselves anymore.
That's why one should allow themselves get addict so they won't get to a point where it's uncontrollable a point where they have no choice and can't help themselves like you stated, I think the OP is right to say it's a choice cause it's every gamblers decisions to avoid those things that would get them addicted at the first place but then they refused to gamble responsibly and allowed it get to a point where it becomes uncontrollable, one thing most gamblers that got addicted lack is self-control and discipline cause those are the traits that could help one monitor their gambling habits and also avoid getting addicted, I'm sure that even most casinos indicate that gamblers should gamble responsibly so why should any gambler decide to go against that or do they know more that the owners of the business?
We are on our own when we decide. We can't put the blame to the casinos when we become addicted because they didn't forced us to gamble.
When someone is trying to find fault from the others, that's one great sign that person is totally addicted and looking to put the pressure onto others but not willing to admit his own fault.
Most addicted gamblers are like that and undenying because they don't want others to see them as is and that's the hard knockout for them to accept that reality.
Of course, the casino should not be the party to be blamed for any downturn experienced by gamblers, because however, as you said above, there is absolutely no coercion or even threat from the casino to make someone gamble, meaning it all depends on the gambler's own wishes and desires.
A gambler who tries to find fault with others? yes it is possible especially when they get some criticism from other people regardless of people who are also involved in gambling or not, it is their way of diverting attention, or meaning it is an action that can indirectly make them safe of several accusations related to facts said by other people regarding him.
Considering that gambling has a bad stigma in most societies, yes, of course it is very possible for a gambler to hide their addiction to gambling from other people so that they can escape various criticism.