It seems very clear to me that a page that promotes the removal of Facebook ads, via its software, fits squarely in violation of the agreement.
Facebook seems very reasonable in this -- they're giving him a second chance, after blatantly violating the terms of service. And yes, it is blatant. Anyone who thinks that removing Facebook's ads are compliant with the Terms of Service is living in the world they wish exists, and not the one that actually does.
And if they have a problem with that, surely they would have sued AdBlock Plus by now. Right?
Personally, I think they're full of it. I'd at least wait until you get an actual letter from their lawyers before making any decisions.
If they apply this rule to individuals who alter the way the site appears to them, they are opening a can of worms. There is no way they consistently enforce this.
I think this is too broad to be meaningful. I sort of get what they're getting at ("don't post broken Javascript that fucks up the page for everyone"), but it's not what they wrote. What they wrote is laughable.
All I can say is: I hope you prevail in your battle. Content creators have absolutely no right to tell users how to render the HTML they deliver; the HTML is advisory, not mandatory. If you want to control rendering, buy a billboard.