that's tough for sure welcoming....the best thing i could suggest is, let them be for now.  the reality is, if he's continuing to be defensive about it, you won't gain many points or much ground talking about them.  you'll probably have to address the 'advice' they are giving him without addressing them ya know?  you'll probably have to be a bit strategic in terms of how you don't touch them or talk about them, but talk about the marriage and the truth of what recovery looks like.   maybe your therapist, counselor, etc will address them so you don't have to, eventually anyway.  i do know the more you talk about 'them' the more he will clam up, not talk rationally and then defend them.  it's like when the betrayed trashes the ap, the unf spouse then sticks up for them as it's an attack on the unf spouse as they had an affair with them and has feelings for them of some sorts.  it's complex. but know that if you're critical of his friends, he's always going to stick up for them as they are 'his friends' and to him it's an attack on his wisdom or choice in friends.  i hope that makes sense and somehow helps you.