A Fable of Science and Politics
I'm not sure that the question of corporate personhood is analogous - because, as you pointed out, the abstract claim (Corporations are people) isn't strongly believed. When laws based on this "premise" gain ground, it seems clear to me that it is not because of most people believe the abstract argument.
On the other hand, if it is true that
"Cynics use theological justifications for their material (occasionally psychological) considerations"
Doesn't it also follow that opposition to these theological justifications would also serve as opposition to the material considerations? If a belief in Social Darwinism can be used to justify eugenics, then mustn't it be a setback for eugenics if Social Darwinism is widely disbelieved?
It seems my argument is this: you can't have it both ways. Either a given 'abstract' belief influences policy and is (therefore) worth fighting about, or it doesn't and isn't. Unless your claim is that all beliefs are held cynically, which seems to me not a possibility worth considering.