He is not debating a real person or group. Sure, there may be individuals/groups who hold those exact ideals as he laid them out, but we don't have any evidence of that. This potential person he is arguing against is the "hollow man'. Because the opponent is imaginary it falls to Berkman to provide the imaginary arguments. Seeing as he is obviously against the position of "the reformer" how can he possibly provide those arguments in good faith?
Per the essay:
If the existing laws have not made you better, he says, then we need more laws and stricter ones.
Without providing an actual opponent who has actually held that belief how can we trust it? Without proof it is an imaginary argument. It might echo provable sentiments of real people/groups, but then why not cite them? Straw/Hollow man arguments rely on fabricating an opponent that closely resembles real people with real ideals, but then giving them weaker arguments and combating those. That is what Berkman has done here with his "reformer" and "prohibitionist".
I also want people to understand something: I do not disagree with Berkman's concerns in this piece. Your paragraph there gives me the impression that you think I am pro "prohibitionism" and opposed to Berkman's position. I am not. Nothing I have said thus far in this thread should lead you to that conclusion either. I am simply against his style of arguing his point. You can agree with a message and still disagree with its delivery, I promise you this.
I have heard this "The Reformer" style arguing before, and it is always bad faith and typically a dangerous point of view to take. This "others" the opposition in ways that make it easier to commit ills against them. Also not referencing a specific organization or group makes it harder for people who fall under the broad description from refuting, and easier to deflect. If your position/argument is strong enough, then why would you need to use shady tactics?