Anyway, given what we know of Orlais and the Andrastian Chantry, I'm having trouble believing the events of Red Crossing were anything more than a convenient excuse to start a holy war on the Dalish, which makes the question of whether the Dalish were 100% to blame for Red Crossing ultimately irrelevant. One of the codex entries you find in DAI points towards this: "The likely truth is that the elves merely wished to maintain sovereignty over lands promised to them by Blessed Andraste herself, when the humans showed clear intent to undermine their autonomy." [...] "The Chantry's response to the elven aggression that resulted in the slaughter of hundreds was predictable. But in light of my thesis, perhaps we should reexamine the events of Red Crossing and wonder if the attack was truly unprovoked. Or whether it is possible that someone saw benefit in sacrificing an entire village to justify the subjugation of an entire people." Anonymous author, pamphlet published by the University of Orlais in 9:12 Dragon. And before you discount this entry on the basis that it's only a theory bear in mind that all codex entries are deliberately written in the game by the devs because they want us to read them. And unlike the differing Dalish/Human codex entries in DAO we don't get the author here, so no obvious hint that this entry is biased.
But even just looking at the history of Orlais and the Chantry is enough to support this. On one hand you have Orlais, who's replaced Tevinter as Thedas' #1 expansionist empire starting in the Divine Age. Among the list of kingdoms they've invaded (successfully or not) are well, pretty much all of them except Antiva, and only because Queen Asha Campana outplayed them by strategically marrying her children and grandchildren into all the important royal and noble families of Thedas, and Orzammar, the world's sole provider of lyrium.
Then you have the Chantry, whose entire purpose is to spread the Chant of Light to all corners of the world so that the Maker can return to Thedas. Having a neighboring country worshipping “false gods” (the first sin according to the Chantry) must be a slap in the face. So they call an Exalted March on the Dales - the first one since the founding of the Chantry. In the Exalted Plains/Emerald Graves we get the following quotes from the memorials “but one last challenge came from the elves, who would not submit to the Maker” and “Sister Amity led the march to the river Tenasir, where stood shrines to the elven gods. These she struck down; standing upon the banks, she sang the Chant of Light. Andraste's Word had come to the Dales, and delivered them from wickedness”. Then Divine Renata I offers peace for the elves, but only if they choose to renounce their gods, embrace the Maker and segregate themselves in human cities.
All of this paints a pretty clear picture of the reasons behind the Fall of the Dales: the Dales are a ripe target for Orlais' expansionist policy, especially since it also gives access to the Fereldan valley (the wiki also says that Emperor Kordillus Drakon I had to put a halt to his expansion into the Free Marches because of pressure from the Dales, but I can't find the source) and the Chantry can further their goal of forcing the Maker on everyone in Thedas.
Tl;DR: Who was at fault in Red Crossing isn't all that important when talking about the Fall of the Dales; Orlais and the Chantry's expansionist policies mean they would have eventually attacked regardless of what the Dalish did.