First, there is the celebrated argument of David Hume that "ought" cannot be derived from "is," that no fact about how things are in the world, however well-established, can logically entail that something or other ought or ought not to be done.
Sustaining the will to do something about it particularly if that something also entails real economic pain or military risks—is quite another.
They know that they need to be ready to do anything to fight against the terrorist threat, even if that entails doing something that's actually inefficient.
Thes error has been corrected.
For the conclusion that it entails, namely, that "There exists something that could have been an F", does not require us to suppose that there is some concrete object that could have been F. Rather, BF requires only the existence of a something that could have been F, and that thing might well be contingently nonconcrete.
For an actualist, from the fact that there might have been aliens (◇∃xAx), BF entails that there exists something that could have been an Alien (∃x◇Ax).
Even if determinism entails that there is something we have in common with things which lack free will, it doesn't follow that there are no relevant differences.
On the natural assumption that beliefs are paradigmatic mental states, the view that phenomenal consciousness is the true criterion of the mental further entails that there is something it is like to have such a propositional attitude as believing that 5 is a prime number a consequence some find doubtful.
This is produced by a self-referential sentence claiming 'If I am true, then ⊥', where ⊥ is a constant (what logicians usually call the falsum) which is or entails something that is also dialetheically unacceptable, say ⊥ = 'Everything is true', the trivialist claim.
Remarkably, he found that a simple modification of general relativity's equations entailed something that would have, well, blown Newton's mind: antigravity — a gravitational force that pushes instead of pulls.
