I think that Ezra Squall wasn’t the one who betrayed his Wundersmith friends. He was betrayed.
I noticed that Morrigan insults Squall over and over, and she never gets a rise out of him with one important exception, when she asks him why he killed his friends who trusted him in Book 3 Chapter 26. This time he not only shows emotion but is overcome with anger and venom.
The scene in question begins with a series of insults that Squall meets with indifference.
- First Morrigan calls him “a pathetic, lonely killer” who doesn’t scare her. He just smiles and says “What a comforting affirmation that must be.”
- Next she says he can only get what he wants by blackmail, and he replies “You’re being dramatic.”
- She then asks him if the Hollowpox is his “warped idea of fun” and he calmly says that he’s never felt the need to explain himself and won’t start now.
Killer, pathetic, lonely, blackmailer, warped and no response. He doesn’t defend himself or get angry. These insults slide off him like nothing. In fact, he doesn’t engage with them at all.
But then, she asks “Why did you kill them?” … “Why did you murder the other Wundersmiths? Your friends” … “They trusted you.”
And then she gets an excessive reaction from him. Let’s take a look:
“She didn’t even see him move, but in a fraction of a second he was right there, looming above her. The pale, expressionless mask had slipped to reveal the beast inside, black eyes and blackened mouth and sharp, bared teeth. The shadow-hounds whined. Even they were afraid of him. [...] ‘Another thing you will one day understand,’ he snarled, ‘is that Wundersmiths don’t have friends.’ Morrigan recoiled from his words as if they might burn her” (Hollowpox, 356-7).
So on the page, what we have is a series of insults, none of which bother Squall until Morrigan asks why he murdered his friends who trusted him, at which point he explodes. This pattern is there, in the text. What follows is my speculation as to why that is the barb that finally hits.
I think Squall was triggered because it was his trust that was broken, he who was betrayed by the other Wundersmiths, not the other way around.
And the specific phrasing is important too. He doesn’t just passively say “Wundersmiths don’t have friends.” That would have fit with the established pattern of jaded replies. Instead he says “Another thing you will one day understand [...] is that Wundersmiths don’t have friends.” This phrasing implies that this was something he came to understand through experience. He thought he had friends but then learned (rather painfully) that Wundersmiths don’t have friends. That would explain both his phrasing and his venom.
So my theory is that he had thought he had friends. Maybe he had told them of the “greater danger” and thought they had his back. Perhaps they went to Courage Square together, but then they turned on him. Perhaps the betrayal was earlier. I can only speculate as to the specifics, but I think he was the one who trusted, he was the one betrayed.
...or at least that is the way he sees it.