This my friend falls under the General Guy Code, paragraph 62b/117:
"You can't ever criticize a friends girlfriend, never ever!
You can agree with him when he does it, but you can never do that yourself!
You can criticize her when, and only when, she becomes the hated ex, then dish it out all you want."
That's how this works mate, so you can't go near the subject, even if she would be a soul sucking demon, you haveto wait for your friend to realize it himself, otherwise you will ruin the friendship.
"You can't ever criticize a friends girlfriend, never ever!
You can agree with him when he does it, but you can never do that yourself!
You can criticize her when, and only when, she becomes the hated ex, then dish it out all you want."
That's how this works mate, so you can't go near the subject, even if she would be a soul sucking demon, you haveto wait for your friend to realize it himself, otherwise you will ruin the friendship.