Cheers the French Chateau entertaining thing has a very logical explanation, and it isn't that the women in the couples wouldn't like it. HR wouldn't like it - too big a risk of an harassment claim. I'm sure
would be the reaction of most people who read that, but it's how it is. The corporate world is paranoid. Much easier to just not have a situation where someone could claim anything untoward.
The main point I have taken from this thread is that despite numerous examples disproving the OP, the single faction is determined that all those experiences are just not valid. I'm not minimising, I'm looking at the analysis on here.
If you believe all married women hate you, and don't want you around their DH's, you are going to believe that whatever I or any other married woman says. It will then become a self fulfilling prophecy. As I said upthread I'd probably not be friends with someone who had thoughts like that about me. I'd definitely not socialise with them. So de facto they'd feel I was excluding them.
As for dinner parties, the kind of people who have formal dinner parties go to endless trouble to find guests who gel. They'd probably stick to the even numbers couple quota. People like me who can't stand salad forks, seating plans and coffee after dessert affairs invite whoever, and if they have nothing in common and all fight, well so what 
I don't doubt people have had bad experiences, but that doesn't mean this is how everyone thinks. When divorce carried a stigma, yes everyone did think like that. It doesn't anymore. What's the current statistic for marriage breakdown? 50%? More? If that was a reason for exclusion no-one would have any friends at all.
An example - I met up with an old school friend who I hadn't seen in about 20 years. When she arrived with dcs but without partner I assumed she was single. Thought nothing of it other than I'd probably made too many scones. She was obviously very awkward about telling me, and told me in a round about way that her mother had said 'but does Worse even know that you are divorced?'. That's a shame.
This isn't an agree to disagree post, it's one that is saying things aren't that black and white.
Interesting thread this. I hope those who feel excluded will feel less so, having read some of the comments.