Bros, I called it 7 chapters ago. The glasses-wearing beta male is actually behind everything. His cheat-skill is some stupid mind control bullshit; cuz he "wants to be the main character."
Nah, he's a shitter the Juumonji (the dude carrying a sword on the back) dude riled up as a mean of distraction when he was about to pull the trigger on the people of the fortress.
Yeah it looks like they are being controlled. Its because of shit like this that they dont like monster tamers, when it should be one of the best powers out there, using monsters against monsters. Guess one time someone did this shit and suddenly they started treating badly all others that had this power.
This whole arc is very dark in the novel. It also lays the foundation for the 'main antagonist' of the story during this battle. Though not sure what I think of the manga version lightening it up in spots. The light-hearted moments are basically non-existent in the novel version. Either that or the scenes play out a little more seriously.