[pope1982]

Sounds like he is insecure, and his jealousy is showing. I don't claim to be perfect, I have had my fair share of jealous fits, but the problem here is his not yours. You can't be there to cater to his ego 24-7 and this was part of your life before he was.

Lines of communication need to be open and clear and relationships needs to have boundaries drawn out clear and agreed upon.
Instead of changing the conversation and letting him hurt your feelings regarding your friend, ask him what bothers him so much about it and tell him how ridiculous he sounds. Offer to let him to talk to your friend to feel him out, Or let him watch the two of you interact.

If he still is not comfortable with this part of your life, after you've invited him to join you in it... you have to decide if this is something you want to wait out and see if there is any change possible in the future, or if you can live with losing that part of your life if it turns out that is not the case.

If he is meant to be your "one", give and take shouldn't come as pulling teeth. It shouldn't require a second thought.