Might Also Be Dabi's Dislike Of Using Children In These Conflicts - Blog Posts

I have a lot of thoughts about why Dabi pretended not to see Aoyama here. It's implied he knows Aoyama is the traitor, but even so Dabi chooses not to mention Aoyama's interference to All for One. And to some extent, it's likely because Touya doesn't trust All for One and he knows they have different end goals in mind. He might have some embers of sympathy considering that like Aoyama, All for One attempted to use Touya because of the downstream effects of his parents' bad life decisions. But then there's also this

The terrified position Aoyama is taking here is something Touya would be more than familiar with as well...