The most disturbed I've ever been on a plane have been situations with crying babies/toddlers and really loud obnoxious adults. Pre-kids, the babies annoyed me because I had no clue how difficult it is to keep a baby quiet on a 10 hour flight. But it's not like they can really help it. But the adults who are very loudly talking and laughing until 4am on the plane...they know better! They are the ones being obnoxious and inconsiderate. Yet, no one gives them dirty looks when they come on the plane, like the wary looks my (relatively quiet) kids get.
The bookstore thing bugs me, because the bookstore is not the library. It's a place where people are supposed to buy things, not sit in chairs and read stuff for an hour or hog the cafe with their laptops for the price of one cheap cup of coffee. People treat it like the library or their personal office and it's not. My kids may not be talking in whispers but at least we're buying things. That's a personal gripe of mine...I expect my kids to hold hands, walk and be relatively quiet in the bookstore but there's no way I'm asking them to whisper for the freeloaders.
I have seen some pretty poor child behavior in public and I blame that on permissive parenting. I think it's pretty selfish of the parents. We all want to see the newest R rated movie, but if you can't get a babysitter, please don't take your loud baby or traumatized child in the cinema. I had to skip movies when my kids were too little to be there and it didn't kill me to wait for it to come out on video.
OTOH, people are pretty unfriendly to children in some public places. Here is my gripe story. We eat at Panera Bread, because my kids like the bagels. They sit in their chairs and they eat quietly. Their only offense is getting the cream cheese all over their faces.

They are, honestly, very quiet and respectful, however. But every time we've ever sat down, the people with laptops (the ones who are renting Panera as office space for the price of one latte) get up and leave immediately. You know, it annoys the crap out of me to have to hear their loud self-important phone conversations on their cell but I'm not leaving over that. But I enter with my quiet boys and the very sight of them drives the laptop people away.

. The last time it happened, the boys sat down and started talking...a laptop guy immediately sighed deeply and packed up his stuff. I was so pissed off over his sense of entitlement. We're spending over 10 bucks for a 20 minute period and this guy is spending about 3 bucks for an hour with his laptop. And yet, we're considered the intruders. We're freaking paying customers!

: Now, having said that, I wouldn't bring my kids into a darkened coffee house and let them talk really loudly, because that's a self-selected group that shares an understanding of what the environment is supposed to be like there...hushed. But Panera Bread? Give me a freaking break!
Pre-kids, I was one of those annoyed people who cringed when children did more than breathe in public. Post-kids, I'm one of those annoyed people who simultaneously hates permissive parenting but hates having her children treated like sub-human creatures.