Couldn't he submit a pull request with the rule out explaining his reasons?

I didn't know EasyList had advanced AI to differentiate between 'one-line, textual "sponsorship" banner' ads and other ads, nor that its stated goal was to block some ads but not others. I'm quite sure if the latter ever becomes true, it'll stop being used by reputable ad blockers. Until then, the list is working correctly in respect to this ad like it works correctly in respect to other ads.

A sponsorship message is an advert. Easylist is working as intended. The "acceptable ads" program is an entirely separate whitelist and it makes no difference if the advert meets those criteria.

It's still an ad. Calling it a sponsorship doesn't change that.

Granted, it's an unobtrusive ad (at best), but it has every reason to be filtered out by a gosh-darn ad-blocker.

That's kinda silly even if people may technically view it as an ad.