A popular tactic in Catholic apologetics is to quote-mine the church fathers for statements that coincide with Roman Catholic dogma. There are potential problems with this appeal even on its own grounds. There's the danger of reading later developments and later interpretations back into these early statements. The risk of recontextualizing the original in light of subsequent developments, where you transplant a statement into a different theological framework.
For instance, an apologist like Newman may treat these statements as seminal claims ripe for further development. The beginning of an ongoing process which will reach fruition centuries down the line. From acorn to oak. But why assume the church fathers viewed their positions as merely seminal? What if they never intended to take it any further than that? What if that's where their position begins and ends? What if that was their complete position?
ii) But beyond that, there's another problem. To my knowledge, Benedict XVI and Archbishop Lefebvre share many theological positions in common. You could read pages of each and not see any difference. You could arrange their theological positions in parallel columns, where they match up on doctrine after doctrine.
But, of course, that would be deceptive, for despite their extensive theological commonalities, there was a major rift in their respective theological outlooks. Lefebvre became the leading dissident, on the right, of Vatican II. Their dissimilarities are at least as significant as their similarities. Despite having so much in common, Benedict XVI and Archbishop Lefebvre move further apart. They are ultimately defined by their theological divergence rather than convergence. They aren't moving toward a common destination, but in opposing destinations.
In principle, Catholic Answers could quote-mine Lefebvre to attest Roman Catholic dogma, just like they quote-mine the church fathers, but that would be misleading and underhanded, because Lefebvre sharply diverged from official developments in Catholic theology in the 60s. Likewise, there's no reason to think church fathers, even those with "proto-Catholic" sympathies, would side with Pope Francis rather than Archbishop Lefebvre.