Yes, unfortunately, the Roman church teaches its members that it is infallible and cannot be questioned. The Roman church then becomes the measure of all things in a practical sense.
In some respect the church itself is worshipped, along with Mary and the saints.
Certainly, the magisterium decides WHAT scripture is, WHAT tradition is, WHAT the interpretation is. To say that the RCC is not above scripture or anything else rings a bit hollow when practice is observed.
For she has "infallibly" declared she is and will be perpetually infallible whenever she speaks in accordance with her infallibly defined (scope and subject-based) formula, which renders her declaration that she is infallible, to be infallible, as well as all else she accordingly declares, including support for her claim.
While RCs attempt to support traditions of men with Scripture as if the weight of Scriptural substantiation from that was determinative of doctrine, and provided certain assurance of truth, this cannot be the case as that would make them as evangelicals.
Rather, the only authoritative interpretation of Scripture, history or tradition which they may invoke for support is that which Rome gives, and thus the RC's real assurance is based on the premise of Rome's assured infallibility, and their goal is to bring you to cease from objectively seeking to ascertain the veracity of her teachings by Scripture and to trust that in the veracity of Rome for assurance.
So THAT's where SLC got the idea!