It is common for an active CG to be***ve they are in control and sadly it is only those who are looking on who realise they are not.
This is not the professional way of dealing with you son’s addiction but many of us have used this method and found it helped in communication.   Imagine your son’s addiction as a slavering, vicious beast in the corner of the room when you talk to him. When you don’t threaten his addiction, hopefully he can hear you.   When you threaten the addiction it leaps between you and from that moment on your son only hears the distorted addiction and not your words.   In turn, you only hear the the ***s, the manipulation and deceit of the addiction and it can be very loud and very nasty.  
The addiction is the master of manipulation and empty threats from the non-
CG are like a green light to it.   Whatever you say you must be prepared to carry out.
I expect you have found yourself in the middle of an argument and not been sure how you got there – if you have it was undoubtedly caused by the addiction that thrives on confrontation.   Your son’s addiction causes him to feel a failure and worthless, so when you say you love him and you are trying to help him, his addiction is saying – don’t be***ve them, they don’t understand, you are worthless but if you indulge me – I will give you what you want.
You are fighting an unseen enemy but I be***ve that by giving it a persona we learn to tackle it differently and confuse it.  
Your son’s addiction is a secretive addiction that creeps up by stealth. When he first gambled, he probably won. It was a sociable thing to do, after all many people do it and have fun.   He couldn’t know that, for him, addiction was waiting. Unfortunately by the time it is recognised it has done its damage and only the right treatment will help the CG control it.
I would imagine you are feeling very lost and weak in the face of this problem.     Know that you do not own the addiction to gamble and therefore you are stronger than your son who is controlled.  
First posts are always about the CG and never about those who love them. Coping is hard but important because when we crumble the addiction wins and we are powerless.   It is important that you stay strong and united; sharing with family members or those he might seek enablement from is often good.   It is impossible; I think, to know what it is like to live with the addiction to gamble, unless you have been there, so often those we turn to offer opinions that do not help. I be***ve it is good to get knowledge and then to tell others as a statement rather than a question.   Support is good however, (although not always possible) among his siblings.    
Your son’s addiction will have made him emotionally immature. Just as a child, caught out doing something it should not, your son will have **** to cover up his addiction.   Every time he was caught or accused he would *** again and the ***s can be very elaborate.   Every *** added to his distortion until his memory became befuddled and his ***s become his truth.  
I would not be writing on here if I did not know that this addiction can be controlled and wonderful lives lived out as a result but the early days of learning feel pretty doom laden as you try and make sense of the senseless – but there is plenty of hope or I would not be here.   I think that maybe it is better not to try and make sense of the senseless.   I don’t be***ve we can ever know what it is like to own an addiction.
Your son cannot show remorse and possibly feels none. His addiction will have moved on from whatever damage he has caused because to admit to the wreckage would be to take responsibility for his behaviour and he is not ready to do that yet.
Your son is not deliberately hurting you. As his parents, you are the closest to him and the ones from whom he will hope for the most enablement.     My CG has told me that as long as I enabled he couldn’t help me understand because to do so would have stopped his enablement.  
As your son is familiar with GA – has he seen the 20 questions?   They are often an eye-opener to a CG.  
The chances are (and I am not judging) that your son has not stopped over the past several years but the addiction is getting stronger and less easy to hide. Was the therapist a dedicated addition therapist?    Did he go to GA for you or because he thought he had a problem? 
Compulsive gambling has nothing to do with money.   It is the most common misunderstanding for F&F. We understand money and feel this is the crux of the problem but the only thing that matters to a CG is the gamble.   I will bring up my thread entitled ‘The F&F Cycle’ along with this post.   It might help, it has been a while since I first wrote it. 
Gambling causes the CG to drastically alter reality to fit personal perception.   To combat this distortion we often have to throw the book of good parenting out of the window.  Personally I think the exceptional book of parenting makes better reading.     I cannot tell you what to do but I know it is unwise to treat all your children the same.   It is enabling to give cash to a CG child, bail that child out when it is in debt or cover for that child when they should be taking responsibility.   From what I have read you are already doing the right thing with regard to protecting yourselves and that is good.
Dear BB – all I have written is tough and I appreciate that it is hard to take in – it took me months in Gamanon before I began to understand any of it and i am now about 7 years into my recovery.  
I don’t do ‘what ifs’ or ‘if onlys’ they don’t help me or change my past one iota but I do be***ve that the sooner a family unites against this addiction the more hope there is for the CG.   Above all else it is so important that you look after yourselves – this addiction will bring you all the way down if you allow it. Looking after you is the finest way you can look after your son.   If he sees you collapsing as a result of his addiction he will gamble.  
In ‘My Journal’ which is the CG forum above this one, there is a post that has recently been pulled up again to the top, which I think would be good for you to read. It is ‘Anniversary. by Colin in Brum.   I hope it helps you understand.
There is an F&F group tomorrow at 22.00 UK time and I would be delighted to welcome you into it.   Nothing said in the group appears on the forum and we communicate in real time.
Keep posting – writing is therapeutic and I will write more about that next time