I am not sure about the parent vs. childfree debate but I am a parent and I will back you up here…it is incredibly rude to bring outside food into a restaurant (with the exception of allergies etc. where there is literally nothing in the place that can be eaten and it has been okayed in advance by the management and possibly a small bag of cheerios or something similar for a baby or toddler who simply cannot wait until food is brought to the table, and again cleared with the management). If for some reason the children couldn’t or wouldn’t eat the food, the proper etiquette would be to get the take out from McDonalds, and then get the take-out Chinese for the parents all to be eaten at home or leave the kids with a sitter (or have someone take them to McDonalds) while the parents dined at their restaurant of choice.
That is so true (and sad). My oldest was born in Texas and he started going out with me and his father from birth (to casual places and only when he was well behaved etc.) By the time he was old enough to eat food he had already tasted a lot of the Mexican foods that his Mommy loves. Yet every time we took him out (when he was old enough to eat) the wait staff tried to force boring “kid food” on him. He loved the spicy stuff and would have eaten bowls of salsa if I had let him (too acidic for his tummy so I did limit quantities) and the staff was always surprised when I declined the grilled cheese sandwiches, hot dogs and french fries in favor of letting the boy have quesadilllas and salsa or tamales (very smushable!) or whatever other delicacy I was eating. One time our waitress actually called everyone else over to the table to “watch the baby eating salsa!”. He was always a good eater (and not too picky) but always has had a preference for spicy and it was commonplace to us, but these waitresses had never seen such a thing. I think it is sad for their own children who are probably being raised on chicken nuggets and french fries.