Keep in mind the following, and look at it from another perspective...
"We" are mammals.
We, continually, find ways/tools to eat OTHER mammals (elk/beef/sheep/deer/pigs/goats/etc...) regardless of size.
Now, we, (land based mammals) have found a way to entrap and eat (process) mammals much larger than our own size. That is what we do. And, the last time I checked, a bull elk was a heck of a lot bigger than the average human.
Why would you think that in nature things would be any different? Your angler has found a way to process large quarry, and it really doesn't give a damn how much you paid for it's lunch/snack.
If it can fit the target in it's mouth, and process it, then it really doesn't give a damn if it was a $1 fish, or a $1,000 fish, it will make it lunch, period, end of story.
If you want to keep the angler, then it's tank mates better be too big to even CONSIDER fitting in it's mouth, or you need to select cheaper tank mates, as they're nothing more than food in his (your angler's) little world.
You have a serious Hoover in your tank, and it WILL suck up anything that it can. Period.