Or that of their teachers....it's the same with cults and all false religions. Just tweaked to suit their own program of indoctrination to retain, maintain, and recruit their memberships.
Unfortunately they include enough of true Christianity into their teachings which baits many who either have already ship wrecked their faith or have little to begin with. ..and especially those unfamiliar with the scriptures themselves.
I will say however, that the deceit that is happening today is especially tricky to spot....True Christians have become especially able to pick false teaching out that the enemy of men's souls has added to his arsenal by using popular or well respected men and woman to deliver a false message.
We see this in the Emergent Movement today. But Catholicism has always been so. Mingling truth with their own teachings to grow and retain the revenues and membership that sustain the hierarchy and priesthood.