Eh, I don't know if I'd be worried necessarily. While the situation definitely sounds odd. It almost sounds like he's beefing over the principle that another person is dictating who he can or cannot be friends with. To that extent it has nothing to do with you at all and everything to do with principle.
Granted, from your vantage point, you think he's fighting for her, which admittedly, is what it looks like. And its got to be weird to watch your man fight for another woman's friendship. So I get why you'd be worried (assuming you are).
If I were you, I'd just talk to him about how it makes you feel. I'm sure he'll eventually understand even if he doesn't at first. Let him now how it looks and then reverse the situation on him. That usually seems to work on folks.
If he said he doesn't have feelings for her anymore, then you have to accept that as truth. I will say that I tend to be one of those people who thinks that for feelings to go, something has to happen to make them go, though.
So here's my diagnosis: don't worry, but talk to him about it anyway to clear the air.
I have found that when you are serious about someone - you tend not to prioritise the friends or exes who you used to sleep with/ have feelings for over your present relationship. I've seen people make a big show about this - trying to integrate their past and their present - maintaining that these friendships are SO important to their lives to the point where they are willing to fight the bit over it and lose the person they love over a silly principle. As i get older I realise that I need these friendships less and less - their importance does not matter to me like it used to - and what does become important are the decisions I make and how it will affect my partner and my family. It's not the nicest thing having to be in a position to chose - but at the end of the day - I would not be willing to sacrifice my relationship for a friendship with a guy I used to f**k/have feelings for - nice guy and all that but .. if he's making my dude uncomfortable then i'm choosing the guy who i get more satisfaction from - the guy I want to be around with forever, who I see a future with and the relationship that I'm working on and that makes me happy.
If this girl has chosen her BF over her friendship with your guy - then your bf needs to back off and show respect for her relationship and for the other man. At the end of the day - if she wanted to keep her friendship with your BF there would be no stopping her. But she hasn't. And that's pretty crystal from where I'm standin'.
Where you stand on all this is up to you. Only you can decide how comfortable you feel in this situation.
Very well said!
And you're right--the boyfriend needs to back off, as this is an issue between the other girl and her partner. The boyfriends needs to realize that the other girl's partner is not telling HIM what to do so much as he is asking HER to do something for him. And that is THEIR own business, so he should mind his, and let this friendship go.