Alcoholism intervention is always a bit of a risk. There is a chance that when you confront someone who is out of control with their drinking, that they will resent you for it and withdrawal further away from you in isolation.
But you have to ask yourself: “Does that really matter? Is it worth the risk anyway?” In many cases it will be. If they are truly out of control and headed for big trouble in a downward spiral, then you may as well just risk it. If they are digging themselves into greater and greater trouble, such as by losing a job or losing key relationships in their life, then there is not much to lose by trying to confront them with a big intervention.
In some cases a person is not really out of control. They might be a true alcoholic, and they might be headed down the wrong path, but they are still able to maintain quite a bit of control for themselves. If they can still pay their bills and provide money for their own drinking, then an intervention has a greater potential to backfire. They can simply isolate and drink on their own. If they are not yet hitting bottom, and are not dependent on others for their booze, then it is probably not time yet to hit them with an intervention. Why would they listen if they can still hold their life together? The nature of denial is that they are going to cling to the positive stuff in their life. If they still have a means to support themselves and get money for more booze, then you are not going to convince them that they are out of control. Quite frankly, they are not yet out of control if they are able to walk away from you and go continue to drink and continue to support themselves.
Just because you see them headed for trouble, just because you see them headed for destruction, does not mean that they are hopeless and out of control. What you see as hitting bottom might not be the same thing to the alcoholic in question.
If you are preparing an alcohol intervention for someone, then you need to consider where they are at on this scale of manageability. It does no good to argue that they are out of control if they are in denial about it. Your best option in many cases is to simply let them know that you care and that you are willing to help them go get some help when they are ready for it. Let them know that the option is available (for treatment). Trying to convince them of anything more is generally going to be a waste of time and energy on your part.
You have to be careful when approaching someone in such a manner because:
1) It is easy for an alcoholic to resent your attempt to help them, especially if they feel that you tricked or manipulated them in organizing an intervention effort.
2) The intervention can easily backfire and produce angry feelings which may lead to more isolation and heavy drinking.
3) The effort may cost quite a bit both financially and emotionally, and the results could be much worse than what you were expecting.
Given all that, it still might make sense to give it a try if you are desperate enough, and if they potential upside outweighs the risks. If the alcoholic is destructing anyway, it might be worth a shot.