The criteria of having no remaining people who experianced or were affected conflict doesn't make it okay to make sets of something. LEGO Zulu warriors being cut down by Maxim guns anyone? I agree with you wholeheartedly about the Sopwith Camel however, as the focus of the set is on the aircraft itself as a machine, not at all on the war in which it featured. For example, in the Indiana Jones KOTCS sets, Soviet troops appeared here and there, but that doesn't mean that LEGO was producing Cold War sets.
On the other hand, I would be perfectly happy to see some interesting models from 1940s Britain that were used in the war, so long as the vehicle or building was the centre piece of the set, not any battles. Cold War, though is FAR too recent, as many of the grievences and disagreements that were the basis of the Cold War still exist in the modern world. I doubt that many nations would be particularly pleased to see LEGO produce modern USAF equipment.
Pirates and other fantastical battles are fine, as these occurred hundreds of years ago, and the LEGO sets aren't accuarate depictions of any real-life war or even nation. That's the key point, plus, the Pirates line isn't exactly gritty; everyone is smiling, dancing around with cutlasses on desert islands with snappy crocodiles.
Common sense from TBW here. As much as we adults all want LEGO Sherman mineclearers, we're only less than half the market. LEGO is predominantly a child's toy, we're just adults who like to buy it.