How can Craigslist accuse you of violating their terms of use? The act of providing a chrome extension does not use their service. Maybe if this was some sort of copyright-circumvention software covered by the DMCA I could understand it. But this sounds like an obvious legal bluff, no?
IANAL either, but I think it would be against craigslist terms for me to continue to use their website while “providing” my accessibility extension. So I could publish the extension, but I would have to stop using craigslist. Additionally, the Chrome Web Store developer agreement[1] prohibits publishing an extension that “knowingly violates a third party’s terms of service”, so my guess is that the lawyer would then ask Google to take it down since any user of the extension would be violating the craigslist terms and thus (after the C&D) I would be violating the Chrome Web Store terms.
It’s pretty airtight, so I took my extension down.
IANAL, which is why I am asking these questions.