Google's true customers are the people buying ads in the first place. They could care less about publishers.

Banning one publisher (unless it's truly massive), isn't going to have much effect to Google's bottom line, so they err on the side of protecting the 'quality' of places ads can be served, at all costs. This also comes through when you see 'invalid traffic' deductions on your AdSense income reports, as i'm sure almost every account running AdSense does, along with the seemingly random crawler errors mentioned in the article. They don't feel the need to explain themselves, and can withhold the revenue at the excuse of 'protecting' the advertiser's side of things.