I've been guilty of doing this but not so blatantly rude. On airplanes I have a tough time with motion sickness so I try very hard to fall asleep, which can be hard to do with loud or crying kids. I also have back issues and have had bad luck with kids kicking my seat. I've had bad luck getting kicking to stop in the past, even with intervention from flight attendants. Most parents grin and say "what can we do, they're kids!" which is frustrating. Even if kids are well behaved, sometimes they just tend to talk/scream loudly in order to be heard, and that doesn't work for me either. I do use earplugs but with really rambunctious kids, they don't seem to help.
I usually fly Southwest so I have a choice where I sit, and I try to sit in front of adults and away from children. I don't make a big deal about it, but if someone with a child ends up sitting directly behind me I do get up and move. I don't make rude gestures or faces, I don't say anything at all. In restaurants, I think it's a little different because you're not in an enclosed space, and I've noticed that kids tend to be a little more well behaved in non-enclosed spaces. So I give everyone a chance. If anyone, adult or child, is doing something that is so outrageous that it interferes with our enjoyment of our meal, then I think it's perfectly alright to request to move elsewhere. (As long as you're discreet).
I've always tried to have compassion for parents dealing with difficult children - my father taught me that a long time ago and reminded me that we were also young once. With my first little one on the way, I'm interested to see how my behavior changes!