'That' is NOT a 'Thing'! He is a living breathing human being with a name!

Yesterday (Monday the 13th) My fiance and I went see the President at a park in our town, we also took our 15 month old son (Declan). We were standing there, in the crowd, and Declan was a bit of a fussy baby..it was hot and he was hungry, we hadnt gotten his snacks out yet because we were still trying to find a place to stand. Anyways, I was trying to get him to calm down a bit, and this older lady (in her late 50's at least, probably mid to late 60s, even 70s honestly) looks over and says in the rudest tone I have ever heard in my life "Couldn't you have left THAT at home?" I turned around and snapped "wow, rude much?!" and she said "yeah, well those 'things' need to be kept at home for these events" ... I was pissed off so much..this event was FREE, and there were so many people there that it was loud all over..and they had enough speakers set up that you could hear the introductory speakers just fine..as well as Obama. ..not to mention the fact that this happened before anything had EVEN started. I feel I handled it well, but I also feel like I should have said more.. No one should be so rude that they call a little one a 'That' or a 'thing' .. they are living breathing human beings with a name..and apparently unlike this lady, feelings.