Hi everyone! Long time reader, first time posting!
My cousin's husband has been nothing but rude since he married her over a decade ago. He always thought he was better than my whole family because he grew up wealthy and all of my extended family did not.
When they had their first child six years ago, my immediate family was not allowed to come meet the new baby or even see my cousin for months because he was "afraid {we} would get the baby sick". That is what really soured me toward him. My mom is a nurse who works with newborns, so we all have proper vaccinations, flu shots, and most importantly, are very clean people in general (also, if one of us had been sick, we obviously would have never offered to bring them food and new clothes for their baby, it wasn't like we just invited ourselves over). We were the only ones subjected to that (even my other aunt who smokes two packs a day was "allowed" before us (not judging, just pointing it out!)).
My brother invited them to his wedding 4 years ago and the husband sulked, didn't smile in any of the family pictures, and didn't even attempt to have a good time. It was a beautiful, elegant wedding and my sister-in-law's family even brought up his sore attitude at a dinner the immediate families went to after their wedding.
Two years ago, he started fights with other family members on social media, called my sweet mother names when she tried to keep the peace and said that my family was "trash", even going as far as to say the town where almost all of my immediate and extended family live was "trashy" and only "degenerates" with low standards and I.Q.s live there" (the town could be improved, like any suburb, but it is a wonderful place to live). I just want to say, while we weren't wealthy growing up, my family has worked hard to get to where we are today (myself and my two siblings were the first in our whole family to attend college (including my cousin's husband) and between us have 5 degrees), and we had a great and happy childhood! You don't need wealthy parents to be happy. I, for one, do not think we would be considered "trash" by anyone's standards.
I haven't spoken to either of them in over two years. My cousin has never explicitly condoned his behavior, but she has never even tried to apologize for his behavior. My mom (bless her, really) thinks I should invite them to keep the peace. All of my extended family feel similar to me in not liking him, but no one has gone as far as not inviting the couple to a big family function (wedding, baby shower, etc).
I know etiquette states that if I invite one cousin, I should invite them all. I get along with all of my other cousins and their partners. I just don't know if I want someone who called my family something so awful at my wedding. I don't have a relationship with either of them, so it's not like my life would be any different without them if I chose not to invite them.
If you were me, what would you do?
Thanks for reading my very long post haha! 
