I misunderstood what you meant by wanting a more specific citation. You seem to be short with me; am I right?
Do you mean you'd like me to post what Munificentissimus Deus states? Sure, no problem. It says, by the authority of our Lord Jesus Christ, of the Blessed Apostles Peter and Paul, and by our own authority, we pronounce, declare, and define it to be a divinely revealed dogma: that the Immaculate Mother of God, the ever Virgin Mary, having completed the course of her earthly life, was assumed body and soul into heavenly glory. Hence if anyone, which God forbid, should dare willfully to deny or to call into doubt that which we have defined, let him know that he has fallen away completely from the divine and Catholic Faith.
The RCC clearly states here that God, through the RCC, demands acceptance of the Assumption of Mary on the word of the RCC alone. If you dare doubt the AoM, you are rejecting God. Not a lot of wiggle room for supposed Christians who refuse to believe in the Assumption of Mary, is there?
I apologize for being short, insofar as it seemed you were perhaps avoiding the question or preparing to discount any response short of complete surrender ;o)
Anyway...I think it's possible you may not quite appreciate just how profound an effect "informed consent" has in mitigating the severity of sin. You can see the kernel of this in your citation with the inclusion of the term "willfully." Bear in mind this document was written to the Catholic faithful, and not necessarily formulated with an eye toward Protestant sensibilities.
For a fuller treatment of the Catholic understanding of the culpability of the separated brethren, please see the, admittedly later written, Vatican ll documents.
The RCC clearly states here that God, through the RCC, demands acceptance of the Assumption of Mary on the word of the RCC alone.
Well, the notion that word is insufficient is what divides us, now isn't it?