If you take as a foundational assumption that the brand name in the search string means the traffic is in some sense owned by the brand, then you're absolutely right. It's essentially racketeering. Certainly brands often view traffic that way.
Personally I resist the idea that a brand owns my attention because I used a keyword, but that's one of my many personal quirks.
It's a little dicer in the cases where we can pretty much infer that they're trying to get to a specific thing and would have happily used a direct URL to the page if they had the wherewithal to do so. In this case the ad placement is basically a brand trying to hijack my attention while I'm in the process of seeking a thing out.
I struggle to think of a meat world analogy. It would be something like if I dialed my girlfriend up on the phone and, instead of routing me straight to her, I had to navigate through a switchboard asking me "How about talking to these sexy singles in your area instead?" And in order to prevent this, my girlfriend would then have to pay the company to route my call straight to her.
Of course this isn't a perfect metaphor because there's a lot of different ways people use a search bar, especially now that search bars are merged into URL bars. But that sort of gets at what it is about this that feels sleazy.
I think it also exposes the core problem. The metaphor rests on knowing intent with certainty. It's perhaps possible that certain clarity and pretty much inferring might not always be the same, especially with how search and URL bars have merged.
But I understand completely. If you genuinely feel like you know that person's intent with certainty, someone else having a crack at their attention along the way feels like a violation of your relationship.
Personally I resist the idea that a brand owns my attention because I used a keyword
What kind of keyword are you referring to here? Because brands do own certain keywords, they're called trademarks. If you don't want a brand to feel entitled to your attention, don't include registered trademarks in your search query.
(Yes, I know, trademarks are limited to a specific market segment. Doesn't invalidate the basic premise of searching on trademarks though).
Personally I resist the idea that a brand owns my attention because I used a keyword, but that's one of my many personal quirks.