I have a theory about the general impatience and lack of tolerance people have not only for children, but for any and all habits of others they find annoying. I think it stems from the cultural shift away from public spaces to being home all the time.
I cannot overstate how much I hate when people are dicks about babies crying in public (especially airplanes). Do you think the parent is having a good time right now?? Do you think they are not aware of the situation??? Are you going to negotiate with a literal infant????