Husband getting all defensive over mil

Hi, yesterday we went to a Family gathering. This morning I noticed a few spots on my daughters loops and a rash on this one section of her head ( it looked like she bumped her head at first until I had a closer look) When I mentioned it to my husband I said I wonder if someone might have kissed her or something and she has a reaction or something since eveyone kept on kissing her yesterday. He straight away said IT WASNT MY MUM. ( btw his mum gets cold sores lol) I just gave him a side eye and was like I didn’t say it was your mum ? He was like ik but I’m just saying it wasn’t my mum. I just was like wth I didn’t even say your mum, there was like 10 ppl there and it could’ve been anyone, I didn’t even try to assume it was anyone. It ended up turning into a stupid argument because he just kept on saying well whatever it is it wasn’t my mum. I was like it could’ve been anything! Even someone’s lipstick ( my LO has sensitive skin) but he just kept on insisting it wasn’t his mum even though I never mentioned his mum. I find it so funny because his mum treated me and him like absolute shit,prayed that he dies and burns in hell, made my pregnancy/ postpartum hell and also made horrible comments about our child, literally wished that we get divorced and abused him since he was a kid but somehow she’s sooo in his head that he will go on defence mode even when she’s not even mentioned. It’s all so weird to me honestly 😂😂