AITA for telling my parents that if they ever call my son a "half-breed" again, I will cut them out of our lives?

I had a really hard time getting pregnant. After three years of trying, a dozen failed IUIs, and two failed IVFs, I finally got pregnant the third time. It was such an insane amount of money, and we didn't know if we'd ever have enough to try again. My husband and I were over the moon when we finally got that positive test.<br><br>Then we found out our baby was biracial. I was floored. My husband was just as shocked as I was. We both started looking into paternity tests, but we didn't want to know (I didn't want to risk the baby) until he was born.<br><br>Well, he was born a year ago now. Our paternity test confirmed that my husband is the father. That said, we both now know that he is not actually the biological father. The only reason we know is because the test said it was unlikely that they were biologically related. It also said that the baby was unlikely to be related to my side of the family either. It essentially told us that my husband cheated, and so did I. My husband and I did DNA tests to figure out what actually happened. The tests came back indicating that my husband and I are both European (with small percentages of Middle Eastern and African). But our son has a decent amount of East Asian ancestry, and no DNA from us. I also just so happen to have two East Asian coworkers who both look vaguely like my son. Putting two and two together, we realized what must have happened. My husband had an affair with one of the two ladies, and I had an affair with the other.<br><br>We confronted each other, and we both confessed. Neither of us remembers what happened though, and the timing works out for it to have happened on the same night. It turns out that during a work party last year, we both got extremely drunk, went home together, and "did our own thing". We don't know who the biological father is, and we don't care. We've worked past it and moved on. We both know that affairs happen, and in this case, it actually worked out for the best.<br><br>We named him Alexander (Sandy for short), and he's absolutely adorable.<br><br>That said, my parents were horrified when we told them. They were even more horrified when we told them it was because of an affair. They kept making ignorant comments about how Alexander is a half-breed. I told them repeatedly that he is fully human, and fully my son. The "half-breed" comments didn't stop though, and eventually, I lost it and told them to fuck off. I didn't talk to them for a week after that.<br><br>They reached out to me a few days ago, saying they wanted to talk and that they're sorry if what they said came across as racist. They said they're just worried about what will happen to Alexander because he's a half-breed in a mostly white neighborhood. I told them that it's none of their concern, and if they ever call him a half-breed again, I will cut them out of our lives completely. They told me that I was being immature, but I think I'm being fairly rational here.<br><br>So AITA?