You know... . I can see why this is tough. You want him to encourage you, or at least accept your decision. As long as there is no truth to his feeling that you are trying to manipulate him into going, then your conscience is clean and you don't need his approval to go.
On a related note, I have decided that a face-to-face support group might be a good idea for me, so, I found a local CoDa meeting that I plan on attending starting next week. That's not in leau of posting and reading here, of course, but I thought it might help me. Since I know my wife will be nervous about me being a little later than usual one night a week, I told her yesterday that I was going to start going... . I told her that I didn't like those days when I feel down and needy. Was kind of hard for her to argue with that, I think.
Also told her the name of the group and why I thought it might help me. Her first response was, "what have I done? I'm not doing something right." I assured her that this is 100% about me and how I cope. Her next reply was, "Well, I think you need to go to see a professional" (she's a big proponent of me getting some meds, which I don't think I need). I told her that the group is facilitated by a professional therapist and I would get the therapist's opinion after a few sessions. Now, the conversation went as well as it could. She didn't get dysregulated, cast blame, or anything like that. She expressed some fear, which I think might be that she is afraid that people in a support group will tell me to leave her, which, let's face it, they might, but that doesn't mean that I will. My family and friends have been telling me that for over 2 years now, so a few strangers won't sway me. Anyway, we will see what happens. I expect her to try to interfere with my going to these meetings, even though she seemed supportive. Maybe I will be surprised.
Long story short, all I can suggest is that you tell him that it is for YOU, and you alone. If it makes you a better person, he may benefit too.
Good luck with this! I went to therapy for a few months and it really helped me!