I think it is a bit annoying too.
We regularly travel first/business class. And get filthy looks form everyone because we have small children.
And no, I do not let them shriek/run around/wail their heads off for the whole flight. In fact, the only time that dd1 (6, severe ASD) has been noisy on a flight in recent memory was on leg 2 of our flight to Australia - business class, A380 (for info). Qantas had stuffed up, and we did not have seats together. we (a party of 6) had: two seats together and 4 singles. dd1 was then 4, dd2 was 2. I sat with dd1, and dh managed to swap with someone to be able to sit with dd2. the cabin crew were great, and asked everyone if they would swap to let dd2 at least see me (she was getting upset), and no one would.
the flight took off, and dd1 started to get distressed because she could hear her sister crying. the man across the aisle from dd1 (who had previously refused to swap with dh/dd2) got really narky that she was upset, and told her off. dd1 shrieked. a lot
(serves him right emoticon - dd1 was wearing a t shirt that said (clearly) "I am autistic, please be patient with me", and tried to turn away form him - he leant over further, and told her she should listen to adults, and not be so rude. wanker.).
there was nothing I could do until the seatbelt signs went off, and then we showed dd1 that dd2 was ok.
so yes, she made a noise. but if the airline had not been stupid and split us, and if the rest of the cabin had not been so self-righteously indignant about swapping seats to alleviate distress in a 2 year old, then no one would have been inconvenienced at all.
children are a fact of life, and our money (as a frequent-travelling family) is as good as anyone else's. all we ask is that people do not assume that our children will behave appallingly, and give half a thought as to why they might be acting up (eg a tot distressed at being separated from mum, or an autistic child scared because a stranger is insisting on invading her personal space - he was asked to stop and not talk to her again, or leave the cabin, btw - by the crew, and not as a result of complaint from us)