Since just joining up normally requires you to murder your own finger maiden I would say that they’re off to a bad start. We also know that Mohg’s followers are a persistent enough problem for everyone else that Yura made it his career to defend people against their random murder attempts (although he does have personal investment with Eleonora too), and that Varre and the other white masks were “abducted” to enable the invasions. Being a murder & pain cult that seems to attack random people just because the boss says god likes when people get stabbed doesn’t exactly stand out as exceptionally evil in the Lands Between, but we definitely know they’ve done at least some stuff to warrant opposition unlike the omens

My personal belief is that the sanguine nobles just straight up are the pureblood knights. The language used to describe them is very similar, both they and Ansbach have dextrous duellist-like fighting styles, the pureblood knight medal takes you right to the place with the highest concentration of sanguine nobles in the game, and if Ansbach dies before the Enir Ilim showdown then you get a random sanguine noble as a substitute summon.