(A) allows us to reach a conclusion that a particular course of action is “irresponsible.” But the conclusion of the argument was that making a particular kind of request is being dishonest. Whether an action is irresponsible doesn’t tell us whether making a request is dishonest.

Doesn’t reach the right destination or begin at the right place. (B) allows us to conclude that a course of action is “better” than another. But that doesn’t imply that calling for a worse course of action is dishonest. Also, finding better ways to dispose of nuclear waste might help reduce the harm from use of nuclear power. So, the principle doesn’t trigger.

If we can show that the pro-nuclear (1) called on people to act in a way that will possibly undermine their goals, and (2) the request was based on the sake of those people’s ideals, then we can conclude that the pro-nuclear were being dishonest. The premises establish (1) – the call was for better ways to dispose of nuclear waste, but we know that this would undermine the anti-nuclear’s goals. They want to get rid of nuclear power ASAP, but better ways to dispose of nuclear waste might prolong nuclear power use. And, we have enough to establish (2) – the pro-nuclear’s call was based on the ideals of the anti-nuclear side (the call was to “live up to [the anti-nuclear’s] own ideals”). So, we can conclude that the pro-nuclear’s call is dishonest.

(D) doesn’t reach the right destination or begin at the right place. It allows us to conclude that a particular request is irresponsible. But that doesn’t establish a request is dishonest. Also, this principle doesn’t trigger. We can’t say that the pro-nuclear think finding better ways to dispose of nuclear waste is not acceptable.

The premises don’t trigger this principle. We don’t know whether the pro-nuclear are failing to reveal that their own ideals conflict with the anti-nuclear’s ideals.