Uninviting Guest (long, i apologize)

I can see why you wouldn't want her there judging by her character, and how she presents herself on social media.

Since this is your FH's friend, I would be persistent in having him speak to his friend. If your FH can't see himself getting married without this friend there, then it's important for him to have this talk with him about his wife and how uncomfortable she makes you, and others feel. It's fine to have opinions, but it's another thing when you act negatively towards others just because they don't share the same opinions and views as you.

Married couples are a package when it comes to inviting them, and it's a slippery slope when you decide to invite one and not the other, sometimes resulting in a ruined friendship. Which is why I think your FH really needs to sit his friend down and have a heart to heart.

If his wife acts this way in public around people and not just on social media, then I would also be wary about inviting her to my wedding. I wouldn't want her going around and making my other guests uncomfortable, or offending them.

Definitely uninvite her! It doesn't matter what anyones views/stands/opinions are on anything there are just certain things you should never say to another person out of sheer human decency! Your FH should have a heart to heart with his friend and make it very clear that he still wants his friend there but his wife cannot come and if they have a problem with that then uninvite both. You should not have to worry about some crazy causing a scene on your wedding day!

Uninvite both. You'll have drama either way, but only uninviting her is singling her out and will cause more drama. I would also say her husband is enabling her behavior, even if he himself is not as bad. If in some horrible universe FH woke up one day and started saying all that, he wouldn't be the man I love, and I would call off the wedding, or divorce him if we were already married. I'm not saying the fact they are still together means he agrees with her, but at the absolute least he clearly does not view her behavior as a deal-breaker, or else he'd tell her to stop being a racist and would be appalled at what she said to you. Are you and FH sure you even want to be friends with her husband?

I'm of the "uninvite both" camp.

There is no way to tactfully rescind an invitation to begin with, but it is in poor taste to do so only for one member of a married unit.

Now, don't mistake this to mean that you shouldn't rescind the invite. You absolutely should. The comment she made to you about losing any future child was absolutely abhorrent, and unabashed racists do not belong at any public event, but especially if you have guests who may be a target demographic for her. You have every right - I might even say obligation - to protect your other guests from someone who means or wishes them harm.

And importantly: her husband condones her behavior, which means he also has no place on your guest list.

That last part, 100%. He condones the behavior, whether he agrees with/shares in her opinions or not, because he remains with her. If my husband ever used to N-word, his bags would be on the lawn when he got home, because just as you said, that means he is not who I thought he was or what I thought I married.

Clearly, her husband knows what he married, and he's okay with it. That means he has no place at your wedding, just as she doesn't.

You shouldn't have to risk her insulting one of your guests and based on the fact that she would go as far as DMing someone I'd bet she will esp if you have invited that person. The only issue is you cannot invite the husband and uninvite the wife, so if your FH wants to maintain that relationship with his friend he may need to have a conversation with him as to why this is happening.