I made the claim, in a comment on this post, that swearing off all forms of the principle of double effect (PDE) leads to moral paralysis.
You can check this old post for the four-pronged PDE as I know it. I referred in the comments to "all forms of the PDE" because others may have their own prongs, but the basic idea of all forms is that, under certain circumstances, an act with foreseeable bad consequences can be morally licit.
So to swear off all forms of the PDE is to insist that acts with foreseeable bad consequences are never morally licit.
By "moral paralysis" I mean something like "lacking morally licit means to a licit end." In acute cases, the moral paralytic is pretty much literally damned if he do and damned if he don't: anything he can do is immoral, and not doing anything is also immoral. In milder cases, moral paralysis is more like extreme rigorism, preventing the sufferer from doing rather common things the Church has never forbidden.
How does swearing off the PDE lead to moral paralysis? Consider the following examples:
Foreseeable Bad Consequence
Driving a car
Conviction of the innocent
("Jury trials" is more properly "formal cooperation in a criminal justice system that uses jury trials," but that doesn't fit on one line.)
Do those who think the PDE is poobah think it is immoral to drive a car or to use electricity (which also causes pollution)? Do they think medical surgery that results in the patient being in pain and bedridden for hours or days afterward is objectively evil? It seems to me that either they must, or they actually do accept some flavor of PDE (possibly under cover of a very ad hoc notion of "bad consequences").
UPDATE: Post modified to satisfy the persnickitiness of a moral theologian who pointed out that, strictly speaking, one of my examples was incorrect.