I don't have an ADHD child, but my 2e ds has an expressive language disorder which has made social relationships challenging at times (many times actually!). I think it's extremely important to work with your child to give him an understanding of how his behaviors impact social situations, and give him tools and techniques to deal with his challenges in social situations. I don't focus on "this is happening because of X" as much as "this is how you deal with xxx" when working through how to get through a specific type of social challenge. However, we also have talked about how this is related to his disability, just in the sense that it gives him a context that it's not something intrinsically "wrong" with him. Whether or not it was related to his disability, I believe that it's important to let a child know that this is something they have the power to learn how to deal with and control.
I also agree with aeh's advice, especially this:
Understand yourself, and what settings and scaffolding you need to function at your best in all domains of your life. That's all. Everyone has to, on some level.
My ds had a teacher who used to listen to his struggles but then also remind him that "everyone has something". This really annoyed me at first because I felt like she was somehow saying that the impact of his disability didn't matter.. but what she was really doing (and what *did* happen) over time, was giving him the insight that it's not just kids with expressive language disorders that struggle, that everyone for the most part has something in their life that they have to work at, and that you work through it and don't let it define you. You work through it and move on. That message, which was difficult for *me* to get, really did get through to ds and it is probably the most helpful thing that any one teacher ever did for him, even more so than any help with all of his actual challenges.
Sorry I'm getting a little OT there - but the main idea is, yes, we acknowledge that the disability causes "x", but we don't let the disability be an excuse or let it define who ds is. Hope that makes sense!
Best wishes,
polarbear