I was thinking of statements attributed to Pius X here , and assent is called for to more than formal statements.
More on this issue here on another thread, by God's grace.
“Even if [the Pope an incarnate devil], we ought not to raise up our heads against him, but calmly lie down to rest on his bosom... He who rebels against our Father is condemned to death, for that which we do to him we do to Christ: we honor Christ if we honor the Pope; we dishonor Christ if we dishonor the Pope.” —Catherine of Siena