Sometimes the big picture is about the little things. As I am a GM at the moment I am constantly reminded there are those ever present gripes that are still pursuing me for which I have come to develop a thick skin but never really turned and faced. That is not to say that I am exactly the same when I am playing of course but the familiar tweets of "surely we would have known this" or "we would have packed this item" or "we wouldn't have done that" still drift across the table. There are many GMs that take a hard line on this sort of back talk but I think these are fair questions to a degree in general, but when there is a critical event or a plot turning point then it can be an awkward moment for a GM particularly if one has to revise a round or briefly step back in time. For my part I tend to play it by ear which is what most GMs do I think but there is a slippery slope.
Broadly speaking there is the unwritten contract of social norms and I certainly don't mind perspectives from a characters point of view but the first signs of nit picking must be clamped down on but equally it will be useful for the GM to throw out the odd bone in an even handed context such as the discovery that the party is being spied on, or the party's weapons have been interfered with etc etc. To be fair to the players if they have been used to hack and slay adventures for too long then the intrigue of a city environment may be lost on them. Its also worth noting that players can put both of their feet in their mouths on occasion as if they are not consistent with NPC interaction and they quickly forget what they may have said then there can be consequences- basically if you are going to arrest your players in the game the read them their rights first.