これでこそ vs これだ use in this sequence


[![enter image description
here](https://i.stack.imgur.com/TQa96.png)](https://i.stack.imgur.com/TQa96.png)

I'm stumbled on the actual nuance of this sentence.

In the top sentence, the character says that if しき is not with them then it's
not "everyone". To which the third character adds これだよ.

Then the third person adds...

これでこそって思ってるくせに

Which I assume is "You are thinking これでこそ, and yet"

I really can't seem to make sense of why he'd correct him over これだよ. I assume
here is "これでこそ" like "with this for sure". "That's how it is." vs "That's how
things should be"? would be my reading but I'm not really convinced.




Is this character named アーロン superficially cynical, uncooperative, or
tsundere-like in nature? In that case, これだよ can mean something slightly
negative like "Oh brother", "This again", or "Come on, I knew this would
happen", rather than "This is it!". If the game is voiced, please pay
attention to his intonation when he speaks.

On the other hand, これでこそ ("This is it", "This is precisely...") is part of a
phrase これでこそ◯◯だ, which is a positive expression used like so:

  * これでこそチャンピオンだ！  
This is what makes him a champion!

  * これでこそ冒険だ！  
This is what I call a true adventure!

So it seems to me that アーロン said in a somewhat low-spirited tone, "Ah, this
again", and is behaving as if he does not agree with the others on the
surface. And then モクマ pointed out, "But deep down, you are happy about it too,
aren't you?" Does this fit the context?

