As the post indicates, Thomasmonopoly's account wasn't disabled for something like misusing AdWords; it was an investigation of potential child pornography. Thomasmonopoly himself says in his write-up that "I too found the image bordering on the limits of what is legally permissible and hoped to highlight the fact that it is allowed to exist within a grey area of legality."
Google has a zero tolerance policy for child pornography. I am glad that Thomasmonopoly got his account reinstated after a full investigation, but it's also incredibly important that Google takes appropriate action on potential child pornography, and United States law compels companies to react to child pornography in certain very specific ways.
For what it's worth, I got a chance to do a question and answer session with some congressional staffers earlier this year, and one of the things I said was that (in my personal opinion), current laws on child pornography were suboptimal.
Here's a quick example from a few months ago: http://www.winknews.com/Local-Florida/2011-04-29/Fla-Senate-... "The Florida Senate voted to extend the state's anti-child pornography law to include not just possessing but also intentionally looking at such images." Looks like the text of the bill is here: http://www.flsenate.gov/Session/Bill/2011/0846/BillText/File... and I don't see any exemption for people who fight or take down child pornography. And that was literally the first link I found after doing a search on Google.
So in theory, looking at images in the process of trying to fight child pornography could be illegal. You don't need to dig far to find similar brittle examples. That's why I'm glad that I work on webspam and not on trying to stop child pornography.