I’d venture to say that the people in the bookstore got less smiley because they are all too accustomed to parents with screaming babies who will not remove the screaming baby from the store when it’s disrupting other customers. If your baby is well-rested and in a good mood, and content to sit in its stroller playing quietly, I certainly don’t see a problem with having the baby in a bookstore.
Don’t see a problem with that, either. Your reasoning that a church Christmas concert would be family-friendly is certainly understandable, and you were being a responsible parent by having an exit strategy. Good for you!! (I really mean that; I’ve been known to positively comment to people that I’ve seen remove screaming children from public venues).
Planes certainly are a different matter. Sometimes you gotta fly somewhere. You can’t take the baby and leave if it starts bothering others. You can have coping strategies, etc. but there’s really only so much you can do.
My guess, as a parent, is that these incidents (most of them) are the result of kids who’ve been pushed beyond their boundaries. If you know your kid can sit quietly for an hour under good circumstances, then don’t expect them to sit for two hours, and for heaven’s sake, try your hardest to make sure circumstances are good! If your child is bored, hungry or tired, melt-downs are that much more likely. If you’re going to take your young child to a museum, do it immediately after a nap and a snack, and plan on taking the child’s cue on when it’s time to leave. Yes, many adults can spend hours browsing in an art museum. But even with all that visual stimulation (in some cases, because of all that visual stimulation), that’s way too long for a small child.
If I wanted to take my young child to a fancy restaurant, here’s how I’d do it: first, we’d have ‘practice’ at home, discussing what tone of voice is appropriate, how she’s expected to sit, etc. Second, I wouldn’t take her for a full meal. Full meals at fancy restaurants take hours. Introduce her to the concept of fancy restaurants, and give her a chance to practice her new skills, by taking her just for dessert (when they’re sure to have something appealing on the menu anyway). Third, I’d take her during ‘off-hours’, not at peak dinner time, etc.
About five years ago, we spent Christmas in Colonial Williamsburg, VA. There was a fancy tea at one of the taverns, and I took mudgirl, who was then five. The day before the tea, I took her out to breakfast at Bob Evans (very family-friendly) and told her we were going to practice our ‘fancy tea’ manners there; we made sure to unfold our napkins and place them in our laps, keep elbows off the table, sit up straight, and use lots of good manners! This prepared her for the tea, and it was a nice afternoon.
Basically, it boils down to the parents. There are parents who simply cannot see that their Little Precious is doing anything wrong, but there are plenty of others who think “Well, if I take her out of here now, I’ll have to listen to her scream all the way home, or I can listen to her scream right here and at least finish looking at what I want to look at”, and that’s what they do, regardless of the irritation it’s causing others. Those parents need to be smacked. Hard. But you certainly sound like the antithesis of ‘that parent’. 
) where Farrah took her daughter for a pedicure. For her first birthday. My daughter is 18 months and still occasionally chews on her toes.