He isn't talking to the people who already use encrypted email. He's talking to those who haven't made up their mind, yet, and since his goal is not to help anyone, but to increase adoption of his favorite solution, portraying the "competition" as hopeless nerds who lost contact with reality, might be an effective strategy.

> personally attacking your audience is not an effective writing technique

Absolutely true. So whenever a writer appears to be attacking their audience, you may have misidentified the audience.