My MIL's Preference for My Biological Son is Tearing Us Apart

My husband and I have two kids, a 5-year-old girl and an 8-year-old boy. After a very traumatic birth with my elder one, I decided I wasn't ready to go through that again. But we still wanted more children, so five years ago we adopted. My mother-in-law cares for our family, but her preference for Malcolm is more than clear. She was furious when she heard I wouldn't be having another biological child and was instantly disapproving. After hearing we were going to adopt, her anger turned into rage. She screamed about how we didn't know the parentage of the child and might end up bringing in someone who would disgrace her lineage. My husband managed to calm her down. Thankfully, when she saw little Julia, it seemed like this was all behind us.

Yesterday, MIL decided to visit us. My husband was away on a trip, so she was just helping around. I was exhausted, so I asked if I could go down for a nap, and she agreed. After a few hours, she woke me up and informed me that she was about to leave. All was good, I was cooking in the kitchen, and suddenly I heard a loud bang followed by Julia crying. When I rushed into the hall, I saw Malcolm towering over her. "You're not real! All of this is mine!" he started screaming. It was incredibly confusing, to say the least.

After calming them down, I asked Malcolm what he meant. He revealed that Grandma Muriel had told him that he was "mommy and daddy's real son." This made me incredibly mad. I asked him what else Grandma had told him, and he shared how she had been telling him that Julia wasn't really his sister and how he should get extra attention for being "extra special." She'd also said he would always be her favorite grandson and more.

Blinded with rage, I blocked Muriel on everything after sending her a text detailing her actions and how this was absolutely unacceptable. I told her she'd never see her grandkids again until they're much older and understand the situation so they wouldn't be swayed by her words. I probably overreacted, to be fair; she is quite an old lady.

After my husband returned, we had quite the argument. To say the least, he disagreed. He adores his mother and told me that stopping her from seeing the kids is inhumane. He said she's simply old-fashioned and didn't know her words would have such a big impact. We will be having a civil discussion about this later.

Honestly, I sometimes wonder what would happen if our family was on a reality show. Can you imagine the drama? Everyone would have an opinion on whether I was too harsh or if my MIL was way out of line. The whole world would be weighing in on our family issues, and the public's reaction would probably be even more intense than what we're dealing with now.

According to you, would I be overreacting if I was on a reality show?