“Catholics are the sole remaining group that it is politically correct to slander and denigrate” Not true at all. Christians, white men, whites in general, Chik Fil A, all are in the cross hairs. Conservatives on campus are another group being targeted.
Christians IN GENERAL can be bashed, true, but Catholicism is sole remaining SPECIFIC group that it is OK to demean in modern society and the mainstream media will let you get away with it. If you SPECIFICALLY attacked any OTHER denomination of Christianity, you'd be ostracized for it.
For example, if you said Lutherans "are a bunch of NAZIs, which is not surprised since their founder Martin Luther hated Jews and told his followers to burn their homes", you'd be immediately get called out for that and the media would demand you apologize to Lutherans.
On the other hand, if you said the Catholic Church "is a pedophile cult that its OK to rape little boys because their Pope just promotes that sort of thing", the media would shrug their shoulders and ignore it. Many would even applaud you for trashing Catholicism.