It's not clear to me why structural protection would be better than self-policing, given that both can fairly trivially be manipulated by a wallet the size of a corporation.
Nobody said it was better. You need both. Ideally, they complement each other in a bigger-than-the-sum-of-its-parts manner that is better than using either one alone.
Tangential example of technology/community interaction: Clay Shirky's "A Group Is It's Own Worst Enemy" is a great essay on how self-policing can backfire even without external influences[0]. The overall conclusion being that the technological framework surrounding the community needs to provide the means for it to support itself not only against internal influences, but also to prevent it from harming itself.
On reddit you can see in practice how the many different subcommunities apply this self-policing in practice, and what kind of effects it has. From the echo chambers of the more extremist ones (won't name any examples to avoid provoking anyone), to examples of subreddits dying due to sloppy moderation not holding back meme-ification and shitposting (same), to communities with very clear goals that are achieved through iron-fisted moderation (usually knowledge-oriented communities like /r/AskHistorians).
Tangential example of technology/community interaction: Clay Shirky's "A Group Is It's Own Worst Enemy" is a great essay on how self-policing can backfire even without external influences[0]. The overall conclusion being that the technological framework surrounding the community needs to provide the means for it to support itself not only against internal influences, but also to prevent it from harming itself.
On reddit you can see in practice how the many different subcommunities apply this self-policing in practice, and what kind of effects it has. From the echo chambers of the more extremist ones (won't name any examples to avoid provoking anyone), to examples of subreddits dying due to sloppy moderation not holding back meme-ification and shitposting (same), to communities with very clear goals that are achieved through iron-fisted moderation (usually knowledge-oriented communities like /r/AskHistorians).
[0] http://shirky.com/writings/group_enemy.html