How should I have responded to this?

Neighbours niece (about 25, mum of the 4 boys, aged 2yrs-8 yrs) was visiting with all the kids (4 boys) and I took my 8mo over to entertain him, he loves kids. We were over with them for a little while, maybe hour and a half, and my boy started to get a little restless, so I gave him his dummy and neighbours niece asked ‘what’s that? why’s he still got that thing??’ And I didn’t know how to respond because I was just so taken aback she’d even ask why I parent the way I do. He has a dummy because it soothes him when he gets upset… much like some other kids have a security blanket.How would you have responded?