Am I in the wrong?

Ashley
Recently, I got into a heated debate with my husband's cousin on Facebook. He was posting a bunch of articles from fake news sites(like resistance.texasnews.news or something like that was the website name) and I asked him if he knew they were fake websites. It was a bunch of anti-Muslim propaganda and I'm honestly just tired of the fake news articles. He responded that h didn't care and all Muslims should be eradicated. I have a lot of Muslims in my family and while I may not be close with them or share their faith- that is still my family. When I explained that to him he said he felt no remorse and will always feel that way. 
Fast forward to today- we're trying to get a head count of everyone coming to our son's first birthday party. SO's aunt replies that she will be there with her son(the racist). When I informed her that he wasn't welcome she went off on me for treating him like crap and how it's not fair for me to exclude him. How he won't have an impact on my child since he's young....never once did she say her son was wrong for what he said. This man is 28 years old and should know better than to speak that way. My husband backs me up 100% and doesn't really want his cousin at the party. I honestly don't even want the aunt to come because it seems he may have learned this hatred from her but she's never verbalized it so my husband doesn't want her to be excluded. 
Long story short- I really hate putting my husband in this position. Should I just allow his cousin to come to keep peace in the family? So sorry this was long and all over the place. I'm a little heated from my confrontation with his aunt.