3.4 speculation

[Theodric]

-snip-

It's a common trope for 'adventurers' in fantasy settings to do anything and everything for a bit of coin or because someone tells them to do it, too. Heck, don't some of the Grand Company hunt bills sometimes include killing Garleans in exchange for seals? Arguably that sort of thing just turns casual slaughter into a sport. As for the actual brainwashing...you're correct in that it is apparently something shown explicitly in 1.0 but - to my knowledge - it isn't shown in 2.0. It is very much like Gridania - the place was a lot more 'horrible' back then but now it's fairly 'light' on the darker elements. 1.0 was in some ways darker overall though - which is something I find myself missing.

At any rate it's worth noting that they were specifically loyal to Gaius and may be stubbornly fighting on his name. He was quite the inspirational figure, it seems, since Livia was especially devoted to him and there's a lot of players who genuinely wanted to side with him back when he made an offer to the Warrior of Light back in The Praetorium. Gaius also had a long string of victories under his belt and, presumably, inspired many of his men to the point where they wouldn't need to be brainwashed.