Yes, before third-wave feminism every man in every relationship got along perfectly with all their wives’ friends and relatives. Those dastardly feminists!
You know, there’s a lot to be said about modern gender roles that isn’t total crap, but I imagine people read comments like this and start thinking the opposite
That's not a full explanation either. We don't know the nature of the conflict. This could be e.g. about jealousy or overall mindset of the poster, but then again, could be (or also be) the friends - one's friends aren't independent random variables. In particular, in a tight clique of friends, people tend to have rather well-correlated mindsets.
(It's an interesting question whether that's by selection or just an effect the group projects onto each member; the distinction being, whether the character similarities would persist after the group dissolves and everyone goes on with their lives. There's likely plenty of studies done about this; if anyone knows of some reliable work there, I'd be interested to read it.)
Maybe it's just me, but it seems that being the man in a relationship has taken a nosedive in value in recent times.