maybe it is because jesus called them out specifically. now are there others yes, anyone who works against the Father could be considered an agent of darkness. You have those who practice darkness outwardly and you have those that mask themselves in light. But all are evil. Some are not even aware of the darkness within their own ranks, and as for the jews, it is all evil from day one. It is just they do not see it for what it is and that is the problem with deception. Goes for christians also, it is not a unique phenomena, but that being said the ones that society has named jew has their hands in a bunch of cookie jars.