Lessons Learned:
- Despite entire fandom constantly talking about the Chaos Gods and threat Chaos poses, most of the Imperial Guard aren't supposed to know anything about it, less alone the specific names.
- Despite their enemeis in Sabbath participating commonly in diablerie and fandom making big deal out of what an unforgivable crime it is, it is not something an average Vampire of Carmarilla knows about in any way.
Oh yes, regular folks in the Imperium are absolutely forbidden from knowing anything about or even talking about chaos at all. The guard may even be sent to fight chaos directly without being told what they're fighting or why, just that they are fighting heretics. And if they ask for more information they will be made an example of so nobody else thinks it's a good idea.
The Imperium is not a nice place to be, mostly
And if they beat chaos, they still have a pretty good chance of getting shot for knowing things they shouldn't.
The imperium has access to mind wipe technology, and has used it for those that survive incidents with chaos or xenos that are considered classified. They can't really afford to simply kill everyone exposed to these things.