I don't think the goddesses dragged the other clans into the war. Stigma was a voluntary alliance rather than a situation where the goddesses just forced the other clans to work for them. This is shown with how Rou's group's betrayal was because of what happened to their village. If they were being coerced to fight, that alone would be a reason to switch sides, and their motives would also be immediately obvious to the fairies and giants who would have been in the same predicament. Drole's reason for fighting was his own and isn't indicative of the other giants. He took his philosophy so far that he actually ended up joining the demons and as far as I can remember he was the only giant to have done so.
I would agrue they were "dragged" in under a false pretense, as we know the reason for the war was not as they portrayed it. It was a power grab. Based on what we know of the giants, I think Drole's reasoning would likely be the case for most if not all the giants, as all they care about is strength. And Drole becoming one of the commandments was also due to word of his bravery being known in even the demon world, giving Zeldris a reason to make the offer in the first place.
To clarify, I'm not saying that the goddesses were blameless in the conflict. They were very clearly overzealous to an extent even greater than what we've seen of Arthur's knights so far. However, that doesn't mean that the demons were portrayed as some kind of victims in that scenario. We've seen them do horrendous things and we also know that the other clans disliked them enough to join the goddesses. Even Meliodas eventually had enough of his clan and killed two of his fellow TC members before joining the alliance. In fact, it seems like pretty much all of the good guy demons eventually ended up betraying the clan, while none of the evil ones did.
It's true we've seen them do horrendous things, but that was in the present, after the terrible stuff during the first Holy War went down. We've strangely not shown them doing anything overtly evil in the past, nor have anything but assumptions on why the giants and fairies were against them. And Meliodas left to be with Elisabeth, I don't think we were shown him having an issue with them beyond their opposition to their relationship. I would argue that those who left were given reasons to do so, not because they dislike their clan or anything. Zeldris would be the best example - we know Zeldris' end goal, peace and being with Gelda, despite him being the commanding force behind the resurrected demons actions. He's willing to do anything to achieve his goal, and only turns against his father when it's established that there is no path to that goal.
I wouldn't use the people shown on-panel as a measure, because Nakaba basically never draws the kind of wide shots where you can really see the scale of the crowds. It's always just some small groups of people and the implication that there are more off-panel. The only real indicator of how many died in total is the scene in the movie where we see the giant graveyard in the ruins of Camelot, the graves numbering at least in the thousands if not tens of thousands based on the sheer scale of the site.
There could be more off-screen, but not that much more given all the free space around. And Nanashi's comment about not being able to save them all would be strange if the majority had died. Plus, if there was thousands hiding underground, that's not something that could easily be hidden.
If Talisker wanted all of the fairies and goddesses to leave the Gorge and never come back, then it's not too surprising that he would be unsatisfied to see a bunch of them still living there. As for how the knights speak, that varies from person to person. Ironside seems like the most zealous of the bunch, Ardbeg hated the demons after losing his daughter but barely mentioned the other clans, Talisker was satisfied with forcing the fairies and giants to flee, and Pellegarde basically just does his own thing. I don't know whether this means that they're interpreting Arthur's desires differently or if Arthur himself doesn't have a clearly defined plan, perhaps because of his weird mood swings.
Until Percy and gang appeared, Nasiens was the only one still living there, everyone else had fled outside. So Talisker's goal had been filled if that was what he wanted. Perhaps, or it could be the situations they were in, with their comments more focus on what they were dealing with. Seeing as they're apparently in direct communication with Arthur, and him seemingly giving out orders, I don't think they could misinterpret his orders. I think, based on what we've seen, Arthur has an overall plot, but due to the fact that his opponents are predicting the future, he's having to make things up as he goes along.
When Anne told the citizens the truth they chastised her for accusing a holy knight of lying, which gives me the impression that they just believed what an esteemed authority figure told them. We know that Nasiens and Ordo used to travel to nearby towns and Donny also somehow made his way to basically the other end of the entire island as a performer in a circus troupe, so it can't be that difficult to get around. It's fair to point out that what people are told isn't necessarily the truth, but I'm not sure that really applies in the case of the Holy War because of how recently it happened and how it engulfed pretty much all of Britannia. You bring up Danafor as an example, but that's hardly comparable seeing how the only people who knew what had happened there were Meliodas, who avoided speaking about his past, and Fraudrin, who wasn't even discovered until later. There were effectively no witnesses to the event, just people seeing Meliodas walk away from a massive hole where the kingdom used to be. Merlin's statement about rescuing the people of Camelot was about the ones the demons were keeping on the surface. She had no knowledge of the ones hiding underground and it's unclear whether she was accounting for the ones who had already been killed by then.
Agree, they appeared to believe him because he was a Holy Knight. That said, if ti was some truly wild claim, I doubt it would only be met with slight disbelief. Going to a neighboring village is one thing, but traveling cross country would be a task. Donny did so, but Donny is also had training. I think it would work, because only a handful of people would have had firsthand knowledge of what went down in the conclusion of the Holy War, and at Camelot, as we know the situation at Camelot was a lot more complicated then it just being wiped out. Everyone else would only know the demons were fought and the war ended. And true, Merlin didn't appear to have knowledge of those underground, though Arthur also seem unable to sense them.
Based on what we've seen, the conflict between Camelot and Liones isn't very overt. They're not amassing their armies to fight in the fields, but instead sending individual knights or small teams to conduct secret missions. It's not the kind of conflict that most people would be aware of or that you would immediately inform any new recruits about, especially when most of them would just end up doing some generic fantasy stuff like killing minor monsters. The thing with Tristan was due to Meliodas messing with him, which the other Sins commented on. It's also not that surprising that young children wouldn't really have a very good understanding of history.
Maybe. Arthur's knights don't seem to be making it any secret to what they're up to. That aside, I would expect someone related to and trained by a high-ranking Holy knight to know something, especially when Howzer isn't exactly tight-lipped about it. Meliodas was messing with him playing the villain, but the sheer lack of any knowledge of parents' feats is quite something.
