I really appreciate you giving a shit. Not sarcastically -- it seems like you're actually doing everything right, and it makes a difference.

Gating robots.txt might be a mistake, but it also might be a quick way to deal with crawlers who mine robots.txt for pages that are more interesting. It's also a page that's never visited by humans. So if you make it a tarpit, you both refuse to give the bot more information and slow it down.

It's crap that it's affecting your work, but a website owner isn't likely to care about the distinction when they're pissed off at having to deal with bad actors that they should never have to care about.