So, CHIME discovers an FRB that's artificial in origin.

How would we know? <- It already could have, I doubt highly that anyone has an answer for how to decipher any meaningful message in a repeating signal from another civilization.

If anyone had any god damn idea how to do that, I'm sure that they'd just shut the fuck up, and not even try.

Because no one will listen. I'm sorry, humanity is stupid. This is true.