I agree with everything you're saying but it's waaaay older than gamergate. If you can find a copy, <em>Waves of Rancor</em> -- published in 1999, makes a compelling case that this evangelical alt-right propaganda has slowly evolved since the early days of radio.
The documentary <em>Q: Into the Storm</em> has a brief scene in episode 5 that is one of the most chilling things I've ever seen. In the scene Cullen Hoback interviews a former psyops veteran who claims to work for retired major general Paul E. Vallely on social media campaigns spreading fabricated info to veterans.
Hoback passes along his phone number and gets a call from Vallely. During the call Vallely pretty much confirms there's an active (unauthorized?) psyop targeting former military. He references a network of former military intelligence and psyops folks working to spread propaganda. He calls them "The Army of Northern Virginia."
The Army of Northern Virginia was the main army of the confederacy during the Civil War. Chilling.