WoT, the codex entry on the Dales, your own arguments. Take your pick.
I don't deny there were racial tensions, but where is the actual source that it was racial tensions that started the war? My arguments are that we don't really know. The Chantry says the elves attacked Red Crossing, unprovoked. The elves say that the humans couldn't let them live as they pleased, and sent missionaries, and then templars. The Chantry says that the elves refused all attempts at trade and commerce. The elves say they wanted to live in peace and isolation, away from humans. The Chantry and Orlais say the elves were kidnapping humans as part of heathen sacrifices, something even Anders questions Merrill on. The elves say they don't, and there is no evidence that this ever happened.
But I can see the elves being self-righteous and arrogant, and quite insulting. I can see some radicals on both sides enflaming tensions. Heck, even if we took the events as told by both sides as true leading up to the war, that would mean that neither the elves nor Orlais actually started it, and it may have easily been started by some radical priests and templars who couldn't handle the elves living in a way that wasn't what they believed. Northern Rivain was put to the sword for the exact same reasons, and it was only localized Chantry forces that did it in Rivain itself, but a slaughter was done in the name of the Maker on the heathen there.
I can see some fanatic Petrice type person in Red Crossing wanting to convert the heathen elves, and when missionaries don't work, she sends templars, stirs up the zealots, and like Petrice does to the Qunari of Kirkwall, enflame the tensions and provoke the conflict.
This is all plausible.
But I have never, ever, said that we know for sure exactly what happened that truly led up to the conflict, because nothing in the lore outright states what happened.
Sure, I can see racial tensions on both sides boiling over and creating the conflict. I think it is quite likely given the climate. The elves didn't help with the second blight, I'm sure many humans felt slighted and insulted. They worship the creators, and the Chantry specifically teaches that the Maker will only return when the Chant is spread to all corners of the world, so that would rile up the religious zealots, and the Dalish had land that Orlais needed, so the powers that be would want the war as well. And the elves, who are isolationists, would be getting more and more aggravated by constant human harassment, legitimate or otherwise, and would have their own factions.
But there is no real evidence or sources that tell us directly what actually went down, so to say that racial tensions boiling over is what causes the war, while likely, is not provable in the absence of evidence in the lore.
Hence why I asked for a direct source that outright says it.