When you tell someone with an addiction that they are harming themselves or that they need to stop, they WILL do more of it - literally because you said that to them. It is a dangerous thing to do. They will not only resent you, but harm themselves even more to counter the rejection they feel you have just done to them.
In personal experience most of the time when people do say these "words of advice they think the person needs to hear". They are doing it for selfish reasons and don't actually wish to help. I know how strange this sounds but the root of their advice it mostly a need to be looked up to by the person or a need to control everything around them. The latter is more often the case.
For example, if you tell a food addict "you should not eat that" they will eat more of it than normal because you said not to. If a person is a drunk, they will get extra drunk that night because of your advice.
You can NOT stop them from doing what they are doing. You can NOT help them unless they ask you for help. Even then most of the time you can't help. The harsh reality is, they like doing what is harming them more than they want to live. That means they like it way more than they like you.
It is a deeply sad thing to watch someone self destruct, but if you care you should shut up and let them be them. If you can not stand to watch cut them out of your life and be done with it. Sometimes helping is harming. Sometimes helping escalates what harm they do to themselves.
I deal with a profound food addiction. I know how much I want to literally eat until I am sick when people tell me how to eat or what to eat. I have learned not to give into this trigger, but most never will. A food addiction is unlike any other as you can't eliminate food from your life. It is harder to get away from.
I also have known many who where addicts of drugs or booze. My brother dank himself out of a family and his health. He will be paying for his drinking for the rest of his life in a care home. I have seen how he would hit the bottle hard as hell every time Mom would say something to him. This was out of love that she said it. She wanted to help, but it did more harm than good.
The sad reality is they have to want to change and even then most literally can't change. They will life "clean" for a while then fall right back into the cycle they where in before. With my personal struggle I have lost over 100 lbs only to put it back on. I have seen people lose 250+ lbs and keep it off for several years, then put it all back on and more. Only two people in my life have every broke the cycle for good. Only 2 out of countless people.
Addiction is an illness of the mind and can't be treated with pills, patches or the like for long. These are stop gap measures and the thoughts and urges are all still there. You can break the physical need but you can't break the desire to give in, or the pleasure it brings to feed the addiction. For the addict, literally nothing on earth compares to this feeling.
Please think about how you treat these people you care about. Please think of the damage you can do them. Realize you could be shortening their lives with your willingness to help. Let them come to you or get out of the way for good. I know how hard it is to watch others do this to themselves. But if you can't just be there for when they need you and let them do this on their terms, then get away fast.
Peace and Love - Dave.