I can imagine that's super frustrating. Luckily we haven't had anyone say this but then I think family learned from her older cousins. Id just keep reiterating that it's not the advice now and you will not be ignoring the official advice.
People are stupid 🙄 🤣
Mine does this too. I found out on the weaning workshop not that relatively long ago the advice for weaning was alot earlier. In the 1600s it was 12 months in some countries in the 1950s it was 4 weeks. I think things being done earlier was the norm to them and like many things they can't understand why it's not the same now. Everytime I mention this my mum's like ugh it's stupid babies weren't just invented but she's not grasping that research has come a long way since I was a baby