I also have to add that there is no reasonable "why" to excuse bombing largely civilian areas. Undoubtably the VC were crossing over the border -- the Cambodian side of the Vietnam-Cambodia border is ethnically and linguistically a mixture of Khmer and Vietnamese, and that border has been fluid up until recent history -- but still most people there would have been civilians.
I'll stick with "an area with many civilians" as my definition of a civilian area. These people weren't wealthy, and it's where they happened to own land and build houses. It becomes a choice between being homeless and impoverished, or staying where you are and taking the risk of being bombed.
If you commit to the idea "I will not bomb civilians", then you offer an enormous advantage to your adversary, who will therefore proceed to make sure civilians are well-distributed in any area of military operation.
