Validity: The passage explicitly states that "given that determinism may well be false, contemporary skeptics about moral responsibility more often pursue a hard incompatibilist line of argument," which directly conveys that hard incompatibilism is a more promising skeptical strategy precisely because its conclusions don't depend on the truth of determinism, and the three premises together support this conclusion.
Confidence: The text clearly presents this as the reason contemporary skeptics prefer hard incompatibilism over hard determinism.