i don't get how it's an argument for encryption if that wasn't the affected part

Huh? It is a argument against government backdoor access to messages.

The government demonstrated that they are unqualified to keep data securely under their control. As such, any argument that a backdoor only allows the duly elected government access is empirically false. Any such backdoor empirically allows nefarious criminals access to your messages whereas the absence of a backdoor keeps your messages safely between you and the other party.

So, your options are:

1. Encryption with no backdoors so all messages are safe.

2. Criminals can freely read your messages so the government can more easily investigate potential criminals.

This website posts a lot of nonsense.