You can recover a scroll written by an Emerald Knight which describes the events at Red Crossing.
There were misunderstandings which lead to conflict and a group of Emerald Knights massacring the town.
Errrm. Nope. That's not how it went. In fact what we learned doesn't even confirm that an actual attack on the settlement ever truly happened. There were two confirmed deaths (elf, later a human girl) that led to a skirmish between elves and humans (the latter attacking, though not without good reason, elves were pretty much standing over the girl's dead body). Humans initially apparently got beaten (possible deaths but it's hard to confirm), but then more came, elves retreated (one confirmed death of the elf that was lover of that dead human girl, possibly other deaths).
That's when the account end. It could be that the incident finally escalated into what ended up being an actual attack on Red Crossing, though it could be also that mentioned events were more bloody than the text suggests - it was an account of what led to the dead elf's death, so the facts that only the most relevant deaths were explicitly mentioned (the first elven girl, then elf's lover, then he himself) doesn't say much. There is at one point a line that reads "The men of the village suspected the girl's flight, and heard the scream. They fell upon the elves, but were no match." - this might imply quite heavy death toll on human side and it could even be that this particular event was first interpreted as attack on Red Crossing and then as ages passed it grew into "massacre of Red Crossing".
So, in the end, we know that Red Crossing wasn't just a story, something happened there. And that the something included a dead elf girl, her sister (literally or figuratively, that's not certain) wanting revenge, star-crossed lovers (both ending up dead) and a skirmish between elves and humans just outside the village. But that's about all we know, the village itself getting attacked isn't even confirmed by these documents. So... yeah, I wouldn't say that Inquisition painted elves as town-slaughtering monsters there 
Although as for Exalted March being justified, that's another story. We can say with great certainty that it was never about Red Crossing, that's some much later addition really. Exalted March was started because a full-on war between Dales and Orlais was going on and Orlais was getting their butts handed to them. Montsimmard was already in elven hands and Dalish army was marching towards Val Royeaux. Which they did capture, btw, before Exalted March managed to halt their advance and push them back.
But I imagine neither side is very comfortable with those details
Neither Chantry nor Orlais would gladly mention "savage elves" sacking their very capital... and Dalish tend to like to put emphasis on Chantry's attempts at converting them and spreading rumors about blood sacrifices to finally destroy Dales. And, well, capturing Val Royeaux doesn't fit all too great 
Basically, it was neither defenseless elves invaded by evil Chantry nor savage heathens conquered by righteous crusade - it was a Dalish-Orlesian war that Orlais ultimately won when the remnants of its army managed to bolster their ranks with religious zealots. I don't think whether there is much sense in talking about "justification" when we know so little about actual goals of elven and Orlesian (including Chantry) leadership. We can judge the results - and those seem pretty ugly, Orlesians kinda outdid themselves with that whole relocation program... But I'd prefer to not judge the war itself. It's possible that humans thought Dales to be weak and underestimated the elves disastrously... Or it could be a preemptive attack by the Dalish, undertaken to stop the threat of Orlesian invasion... threat that could even be completely imagined, mind you. Or not imagined at all, since we're talking about Orlais, after all...
Either way - I don't get the feeling that Dalish involvement in starting the war was really explained, much less demonized.