I've been in situations where I mildly dislike or disapprove of my friends' SO's behaviour, but I never bring it up unless they're already complaining about them, then I go all out and advise them to rethink their relationship (done this recently). The thing is, if they're not being massively hurt (like, not feelings-hurt, but a heartbreak in the making), or seriously abused (which often comes with manipulative tactics, so people aren't to blame for falling for it and being abused), you kinda have to remember that this is who they settled for.
In the end, maybe it speaks more about your friend than just his wife. Or maybe you're just not in the know enough about the situation and his wife is right to treat him that way, or he treats her badly as well. Or you're assuming that your friend has the same standards as you. But yeah, choice of a partner speaks about us too. When my self esteem was low, up to 2 years ago, I used to like absolutely mediocre dudes and I befriended some awful people. Maybe you could show him some fun and open his eyes about how his home life doesn't have to look like that. And go from there.