I see no problem in having a baby out at 10pm (as long as its not regular like) but if its endlessly screaming, get outside/somewhere quiet or go home until you sort it out. Not everyone wants to hear that.
Niall...about the plane thing, its so annoying yes. But sometimes unavoidable. When we went to florida there was a very young baby on our plane screaming the whole way. The mother or father did nothing to attempt to pacify the child. And only fed it once suring the 8/9 hour flight flight too(evidently the only half hour when it was quiet) I felt like going over and throttling them, obviously it was in distress/hungry/whatever and they just didnt care