Boyfriend put his arm around another friend. Is that okay?

My boyfriend put his arm around a friend of mine. I know he didn’t mean any harm by this. I’m certain that nothing is ‘going on’ between the two of them and I dont have any reason to feel insecure about it, but I do; I am going through a stage of depression right now.

I talked to him about it, I explained that I understood that maybe I’m overreacting, being irrational, being sensitive, etc. Still, I just don’t feel like it’s something that I should be ‘okay’ with. It bothers me, especially right now – and I even explained that given another time, when I’m not feeling so down, self-conscious and insecure, I probably wouldn’t have thought twice about it. Still, even then, It’s nothing that I would even consider doing to one of his friends for any reason, what so ever.

I realize that we have two different points of views on this issue, but is this a situation in which I should be more understanding or he should be more understanding? Or both?