It simply doesn't sound right to say which tool a user can use. It's literally the same as arguing that you should be able to block Firefox from accessing your website and it's Mozilla's fault that they don't respect your wishes as a webmaster to block Firefox exclusively. Or that a VPN doesn't publish its IP addresses so that you can block it. Or a screen reader that processes the text to speech in a way that you disagree with.
Philosophically it seems intuitive to say "I should be able to block a third party that is abusing my site" but it's ignoring the broader context of what "open web" and "net neutrality" actually mean.
I run a service for podcasters. There are podcast apps and directories that either ignorantly make unnecessary requests for content or have software bugs that cause redownloads. I could trivially block them, but I don't because doing so penalizes the end user who is ultimately innocent, rather than the badly behaved service operator. The better solution is primitives like rate limiting, which I use liberally. Plus, blocking anyone literally has a direct effect of incentivizing centralization on Apple, Spotify, etc. and making the state of open tech in podcasting even worse.
> the Brave search API allows you (for an extra fee) to get the content with a "license" to use the content for AI training? Who allowed them the right to distribute the content that way?
I don't think there's any court at this point that would back you up that freely published content annotated with full provenance cannot be scraped and published for a fee. Services like this have existed for decades. If you don't want your content scraped, put it behind a login. Especially considering this only applies when you allow other search engines and if you think Google and Bing aren't using your content to train AI, you're off your rocker.