Why would they teach the veneration of Mary? The veneration of Mary comes from our rejection of the teachings of those Christians who denied that Jesus was literally the son of God? The first Marian dogma, the Virgin birth,of course, found its way into Matthew and Luke in the form of the nativity stories and the attendant doctrine of the Incarnation in John’s Prologue. It was finally made totally explicit in the proclamations of the first great councils who insisted that Mary was theotokos —mother of God. The immaculate conception and the Assumption are essentially corollary to the divinity of Jesus, both proclaimed in an age that denies it.
“But though we, or an angel from heaven, preach any other gospel unto you than that which we have preached unto you, let him be accursed. As we said before, so say I now again, If any man preach any other gospel unto you than that ye have received, let him be accursed.” Galatians 1:8-9
Nuff said.