But if you think the writing is a matter of black and white, you're probably going to find yourself disappointed again because Bioware tends to subvert that as a rule.
Have we been playing the same Bioware games? Bioware loves ham-fisted black and white morality elements. It's nuance and even-handedness that they struggle with.
In this case, the war of the Dales though... the question about who is to blame for starting it is pretty black and white. The Dalish have never denied the events of Red Crossing, and now we have the Dales' own historical record to damn them. Red Crossing was an unprovoked act of aggression by the Dales. It was not a response to the theorized Templar incursion or invasion that the forumites invented, it was not a ******-for-tat escalation for ongoing border tensions, it was not a miscommunication or accident, there was no agent provacateur who tricked the Dales into attacking to give Orlais a justification for invasion and conquest.
Red Crossing was the unforced choice of an official Dales military force under recognized Dales leaders who chose to respond to a Dalish elf's free and uncoerced choice to leave the Dales culture and pursue an interracial relation ship and exercise religious freedom by an attempted kidnapping and subsequent massacre. Following this action the Dales proceeded in a major military campaign against Orlais that conquered cities and threatened seize the capital of the nation which.
The only element of all of that which is anywhere close to legitimate and justified would be the Dalish attempting to prevent the elf from leaving. Not on the grounds of culture or religion or interracial relations, which they were completely in the wrong for trying to stop, but because of a concern of the leaking of military secrets... if that was the concern at all. The codex is vague on what sort of secrets they were concerned about. But military secrecy only justifies preventing the elf from leaving- it does not pardon a cross-border kidnapping attempt, it does not excuse the casualties of a massacre, and it certainly doesn't require or imply any need for a full-scale invasion.
The Dales were in the wrong, and the moral and ethical blame for starting the war rests completely on them. Not only did they actually start it, but they chose to take actions that started it, and they started it for bad reasons.
Now, none of that matters what-so-ever to the culpability or responsibility for how the war ended. Dalish policies towards the end of the war is currently vague, and far more responsibility (and blame) for the consequences of how it ended can rest fairly on Orlais.
But as far as who is to blame for the War of the Dales? Who is responsible for starting the second most devastating catastroph in elven history? That's black and white now.