Thanks for the question! So the difference between (B) and (E) is pretty subtle here (I’m assuming you meant B, since that’s the correct answer, not D). So what’s the conclusion of this argument that we’re trying to justify? The conclusion is that there is indeed harm. This practice causes harm. So we need something that points to this specifically. (B) tells us that. But (E) just tells us that a person who convinces someone to take a course of action is in part responsible for the consequences of that action. Sure, they might be responsible, but we need another assumption to get us from the idea of “responsibility” to the idea of harm. This conclusion is about harm, not responsibility, so (E) isn’t enough to get us there itself. Make sure to pay attention to the specific conclusion!
Hope this helps! Feel free to ask any other questions that you might have.